Everything went well except no sound afterwards. I followed the suggested fix:
rm ~/.config/pulse/*.tdb ~/.config/pulse/cookie
but there was still no sound. An extra step was required - I had to go into my audio settings and change the Playback Device from “Headphones” to “Line Out”. Sound is now working as it should.
I have a feeling in the back of my mind that I had to change from “Line Out” to “Headphones” after an update a year or more ago, but I’m not 100% sure about that.
Where can I find this settings?
System Settings => Hardware => Audio
[2021-08-09T11:49:35+0100] [ALPM-SCRIPTLET] -> Running build hook: [base]
[2021-08-09T11:49:35+0100] [ALPM-SCRIPTLET] -> Running build hook: [udev]
[2021-08-09T11:49:36+0100] [ALPM-SCRIPTLET] -> Running build hook: [modconf]
[2021-08-09T11:49:36+0100] [ALPM-SCRIPTLET] -> Running build hook: [block]
[2021-08-09T11:49:38+0100] [ALPM-SCRIPTLET] ==> WARNING: Possibly missing firmware for module: xhci_pci
[2021-08-09T11:49:39+0100] [ALPM-SCRIPTLET] -> Running build hook: [keyboard]
[2021-08-09T11:49:41+0100] [ALPM-SCRIPTLET] -> Running build hook: [keymap]
[2021-08-09T11:49:41+0100] [ALPM-SCRIPTLET] -> Running build hook: [resume]
[2021-08-09T11:49:41+0100] [ALPM-SCRIPTLET] -> Running build hook: [filesystems]
[2021-08-09T11:49:44+0100] [ALPM-SCRIPTLET] ==> Generating module dependencies
[2021-08-09T11:49:44+0100] [ALPM-SCRIPTLET] ==> Creating gzip-compressed initcpio image: /boot/initramfs-5.13-x86_64-fallbac
k.img
I get an error about missing firmware on all of my kernels at the post-transaction hooks part of the update but it doesn’t seem to make any difference. No noticeable issues.
Smooth update.
Edit: After a bit of searching seems this is only an issue for those with a Renesas USB controller. [Solved] Kernel 5.8.0 - xhci_pci / [testing] Repo Forum / Arch Linux Forums
I got the log text from pamac update:
Checking keyring...
....
Upgrading ....
....
tput: No value for $TERM and no -T specified
.......
tput: No value for $TERM and no -T specified
.......
tput: No value for $TERM and no -T specified
......
tput: No value for $TERM and no -T specified
.....
tput: No value for $TERM and no -T specified
.....
tput: No value for $TERM and no -T specified
.....
tput: No value for $TERM and no -T specified
Configuring manjaro-release...
tput: No value for $TERM and no -T specified
......
tput: No value for $TERM and no -T specified
.......
tput: No value for $TERM and no -T specified
Configuring sudo...
.....
tput: No value for $TERM and no -T specified
Running post-transaction hooks...
.....
==> Starting build: 5.10.56-1-MANJARO
-> Running build hook: [base]
-> Running build hook: [udev]
-> Running build hook: [autodetect]
-> Running build hook: [modconf]
-> Running build hook: [block]
==> WARNING: Possibly missing firmware for module: xhci_pci
-> Running build hook: [keyboard]
-> Running build hook: [keymap]
-> Running build hook: [resume]
-> Running build hook: [filesystems]
==> Generating module dependencies
==> Creating gzip-compressed initcpio image: /boot/initramfs-5.10-x86_64.img
==> Image generation successful
==> Building image from preset: /etc/mkinitcpio.d/linux510.preset: 'fallback'
-> -k /boot/vmlinuz-5.10-x86_64 -c /etc/mkinitcpio.conf -g /boot/initramfs-5.10-x86_64-fallback.img -S autodetect
==> Starting build: 5.10.56-1-MANJARO
-> Running build hook: [base]
-> Running build hook: [udev]
-> Running build hook: [modconf]
-> Running build hook: [block]
==> WARNING: Possibly missing firmware for module: xhci_pci
-> Running build hook: [keyboard]
-> Running build hook: [keymap]
-> Running build hook: [resume]
-> Running build hook: [filesystems]
==> Generating module dependencies
==> Creating gzip-compressed initcpio image: /boot/initramfs-5.10-x86_64-fallback.img
==> Image generation successful
Reloading system bus configuration...
Warn about old perl modules
Compiling GSettings XML schema files...
Updating icon theme caches...
Restore Linux kernel modules
==> Warning:
-> Kernel has been updated. Modules of the current kernel
-> have been backed up so you can continue to use your
-> computer. However, the new kernel will only work
-> at next boot.
Changing NetworkManager Connectivity-Ping to manjaro.org
tput: No value for $TERM and no -T specified
Updating systemd-boot entries
.....
A restart is required for the changes to take effect.
Transaction successfully finished.
There are many same logs > tput: No value for $TERM and no -T specified.
I have no idea, what is it? 
but I run the command echo $TERM to show xterm-256color.
On desktop update went smoothly, in laptop update went smoothly after mirror sync. Thank you !
I noticed there had not been an update for any packages in over a week which was strange. I saw this and had it check for new software and again - it found nothing. Looking around on the internet I found the mirrors. The default set of mirrors did not even include any in my own country and apparently they had not updated in a while? I ran a sudo pacman-mirrors --fasttrack which added a bunch of new mirrors including closer ones and suddenly there were over 100 updates available. It is a bit disconcerting that the default mirrors that came with Manjaro seem to have stopped functioning/updating. Might also explain why https://discover.manjaro.org shows very out-of-date software versions?
There is no “default mirrors”. The mirrorlist gets regenerated/updated every week (I think it is) by a systemd-timer when you have pamac installed. If you have uninstalled pamac, you should know to manage your mirrors yourself. 
Nope, pamac is installed. Never unintalled it. There were 5 mirrors originally, most were on the other side of the planet. After running the mirror update there are now 35 including some in my own country.
What’s the output of systemctl status pamac-mirrorlist.timer ?
● pamac-mirrorlist.timer - Generate mirrorlist weekly
Loaded: loaded (/usr/lib/systemd/system/pamac-mirrorlist.timer; enabled; vendor preset: disabled)
Active: active (waiting) since Mon 2021-08-09 07:15:49 EDT; 25min ago
Trigger: Thu 2021-08-12 11:39:20 EDT; 3 days left
Triggers: ● pamac-mirrorlist.service
Aug 09 07:15:49 jim-zb-laptop systemd[1]: Started Generate mirrorlist weekly.
So it would have updated your mirrorlist on August 5th, since the next run is on the 12th.
It still should have had more updates available even with the original set of mirrors. Some of the software updated after updating the mirror list manually was over a week old. It seems like the servers that it was calling were not syncing/up-to-date.
How often a mirror syncs is not in Manjaro’s control.
And according to the announcements on this forum, the last Stable update was on July 28th, which is more than a week ago, so yeah, you wouldn’t have had any updates in the last week, no matter which mirrors you where connected to.
This bug (outdated udev rules that disables important features from nvidia cards: audio over hdmi, USB xHCI Host Controller and USB Type-C UCSI devices) is still present.
Are you sure? As mhwd-db 0.6.5-15 should ship updated profiles.
I can’t move past this point:
sudo pacman -Syyu
:: Synchronizing package databases...
core 171,5 KiB 486 KiB/s 00:00 [################################] 100%
extra 1905,4 KiB 584 KiB/s 00:03 [################################] 100%
community 6,6 MiB 996 KiB/s 00:07 [################################] 100%
multilib 178,9 KiB 1626 KiB/s 00:00 [################################] 100%
:: Starting full system upgrade...
:: Replace jack with extra/jack2? [Y/n]
:: Replace lib32-jack with multilib/lib32-jack2? [Y/n]
:: Replace pamac-common with extra/libpamac? [Y/n]
resolving dependencies...
looking for conflicting packages...
error: failed to prepare transaction (could not satisfy dependencies)
:: installing nvidia-390xx-utils (390.144-1) breaks dependency 'nvidia-390xx-utils=390.143' required by linux59-nvidia-390xx
:: installing pacman (6.0.0-2) breaks dependency 'pacman<5.3' required by package-query
:: installing ruby-atk (3.4.5-1) breaks dependency 'ruby-atk=3.4.3' required by ruby-gtk2
:: installing ruby-pango (3.4.5-1) breaks dependency 'ruby-pango=3.4.3' required by ruby-gtk2
:: installing ruby-gdk_pixbuf2 (3.4.5-1) breaks dependency 'ruby-gdk_pixbuf2=3.4.3' required by ruby-gtk2
Hi !
Cannot update.
With pacman:
erreur : xapp : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
:: Le fichier /var/cache/pacman/pkg/xapp-2.2.3-2-x86_64.pkg.tar.zst est corrompu (paquet non valide ou corrompu (signature PGP)).
Voulez-vous le supprimer ? [O/n] o
erreur : xorg-server-common : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
:: Le fichier /var/cache/pacman/pkg/xorg-server-common-1.20.13-1-x86_64.pkg.tar.zst est corrompu (paquet non valide ou corrompu (signature PGP)).
Voulez-vous le supprimer ? [O/n] o
erreur : xorg-server : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
:: Le fichier /var/cache/pacman/pkg/xorg-server-1.20.13-1-x86_64.pkg.tar.zst est corrompu (paquet non valide ou corrompu (signature PGP)).
Voulez-vous le supprimer ? [O/n] o
erreur : xorg-server-xvfb : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
:: Le fichier /var/cache/pacman/pkg/xorg-server-xvfb-1.20.13-1-x86_64.pkg.tar.zst est corrompu (paquet non valide ou corrompu (signature PGP)).
Voulez-vous le supprimer ? [O/n] o
erreur : yay : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
:: Le fichier /var/cache/pacman/pkg/yay-10.3.1-1-x86_64.pkg.tar.zst est corrompu (paquet non valide ou corrompu (signature PGP)).
Voulez-vous le supprimer ? [O/n] o
erreur : la validation de la transaction a échoué (paquet non valide ou corrompu (signature PGP))
Des erreurs se sont produites, aucun paquet n’a été mis à jour.
With pamac:
Téléchargement de yay (10.3.1-1) démarré
Téléchargement de xorg-server-xvfb (1.20.13-1) démarré
Téléchargement de xorg-server-xvfb (1.20.13-1) terminé
Téléchargement de yay (10.3.1-1) terminé
Vérification du trousseau... [124/124]
Vérification de l’intégrité des paquets... [124/124]
Erreur: xapp : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
Erreur: xorg-server-common : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
Erreur: xorg-server : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
Erreur: xorg-server-xvfb : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
Erreur: yay : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
Suppression des fichiers invalides et nouvel essai...
Résolution des dépendances...
Recherche des conflits entre paquets...
Téléchargement de xorg-server (1.20.13-1) démarré
Téléchargement de xapp (2.2.3-2) démarré
Téléchargement de xapp (2.2.3-2) terminé
Téléchargement de yay (10.3.1-1) démarré
Téléchargement de xorg-server (1.20.13-1) terminé
Téléchargement de xorg-server-common (1.20.13-1) démarré
Téléchargement de xorg-server-common (1.20.13-1) terminé
Téléchargement de xorg-server-xvfb (1.20.13-1) démarré
Téléchargement de xorg-server-xvfb (1.20.13-1) terminé
Téléchargement de yay (10.3.1-1) terminé
Vérification du trousseau... [124/124]
Vérification de l’intégrité des paquets... [124/124]
Erreur: xapp : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
Erreur: xorg-server-common : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
Erreur: xorg-server : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
Erreur: xorg-server-xvfb : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
Erreur: yay : la signature de « Helmut Stult (schinfo) <helmut.stult@schinfo.de> » est de confiance inconnue
Erreur: La validation de la transaction a échoué: paquet non valide ou corrompu (signature PGP):
Execute:
sudo pacman-mirrors --country France --interactive
where obviously France is the country you’re actually in 
and choose the most up-to-date and fast local mirrors and then update your local cache:
sudo pacman -Suyy
and
pamac upgrade
again.