Seems like there is a problem with sddm:
systemctl status sddm.service
Loaded: loaded …
Active: inactive …
…
sddm-helper[786]: [PAM] Closing session
sddm-helper[786]: pam_unix(sddm-autologin:session): session closed for user anthony
sddm[756]: Auth: sddm-helper exited with 1
sddm[756]: Auth: Signal received SIGTERM
systemd[1]: Stopping Simple Desktop Display Manager…
sddm[756]: Display server stopping…
sddm[756]: Display server stopped.
sddm[756]: Running display stop script “/usr/share/sddm/scripts/Xstop”
systemd[1]: sddm service: Succeeded.
systemd[1]: sddm service: Stopped Simple Desktop Display Manager.
If I follow the advice here Failed to start Simple Desktop Display Manager - #2 by bogdancovaciu
system is up-to-date
systemctl stop sddm - takes me back to the screen with output from boot,
startplasma-x11 - returns “$DISPLAY is not set or cannot connect to the X server”
Perhaps it does have to do with this [Stable Update] 2020-11-18 - Kernels, Plasma5, Frameworks, Thunderbird, Firefox, Mesa - #136 by philm after all.
Downgrading sddm to 0.18.1-2 did not solve it unfortunately, but now there is a mouse pointer visible after booting (while the boot output are still visible and nothing else happens)
Downgrading to sddm 0.18.1-3 solved it!
pacman -U /var/cache/pacman/pkg/sddm-0.18.1-3-x86_64.pkg.tar.zst