Okay, try with log_priority=2 added to the kernel command line and see whether that improves things. 
In Grub correct?
Yes and AFTER quiet.
Well, technically he doesn’t need quiet then, because that would suppress all verbosity.
Per default i have there still udev.log_priority=3 inside grub, but i just add your command behind that.
Edit:
@Aragorn
The command log_priority=2 made no change to the output after a restart 
And of course i did also:
sudo update-grub
Here the upper part from my Grub:
# GRUB boot loader configuration
GRUB_DEFAULT=saved
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR='Manjaro'
GRUB_CMDLINE_LINUX_DEFAULT='sysrq_always_enabled=1 resume=UUID=342d34b4-152b-4a04-9479-c0b3cbc6c96f udev.log_priority=3 log_priority=2'
GRUB_CMDLINE_LINUX=""
My mistake — I had to pull up my own /etc/default/grub to check. It’s the udev.log_priority=3 which you should change to udev.log_priority=2.
Still no other output while booting
The 3 red services are still there.
Did you remove the quiet parameter?
What about udev.log_priority=1?
I never re-added it… i posted my Grub output above already.
No difference… i think i have to live with that then
Did you remove the erroneous option? And did you run update-grub again?
By the way, GRUB_DEFAULT=saved is pointless on btrfs, because grub cannot write to btrfs.
You might as well switch it back to 3 then. 
Im using ext4 and yeah i did sudo update grub again and yeah i removed your first erroneous log command right after.
Here the upper part from my Grub:
# GRUB boot loader configuration
GRUB_DEFAULT=saved
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR='Manjaro'
GRUB_CMDLINE_LINUX_DEFAULT='sysrq_always_enabled=1 resume=UUID=342d34b4-152b-4a04-9479-c0b3cbc6c96f udev.log_priority=1'
GRUB_CMDLINE_LINUX=""
I change it now back to 3
I already contacted my Mainboard Vendor (Gigabyte) and they created a NEW Bios Option after my request to disable Wifi and Bluetooth in the Bios. But my Eggs are not big enough to flash on my expensive new Mainboard a Pre-Alpha Bios version 
I’m waiting 2-3 month till the newest Bios is stable and look if i can get rid at least on that Bluetooth error’s. I have a optional bluetooth usb adapter for my X-Box One Gamepad which i only use rarely.
TBH, i never used thunderbolt and i though i disabled that in Bios already.
I would disable that feature in Bios entirely or the Service under Linux, if i could…
Since i have a AM5 Mainboard its also a little confusing to see a thunderbolt info, since thunderbolt is from intel.
With all due respect, but I think @Kobold hasn’t yet decided what he wants. Anywhom, I’d rather work to solve as much of the errors instead of brushing them under the carpet.
Run the @pwx command and give us some more details.
I see that Eric Raymond / Rick Moen opus is more valid than ever, even after 2 decades.
Well i don’t mind to solve error’s… i don’t want to brush anything under the carpet.
If you have any idea how to solve anything, i’m open for that.
Where was your response in this Topic? I couldn’t see you there. I asked there if this output is harmless and they already responsed that it is no problem.
And what command from PWX are you talking about? I posted the journal output already.
You posted a lot of stuff but not the listing from journalctl that @pwx indicate a few posts above.
EDIT:
My bad, I somehow missed it. Let me look
TDX not supported by the host platform
TDX is Intel Trust Domain so if it errors I suppose you are on a AMD machine.
integrity: Problem loading X.509 certificate -22
This has already been mentioned and should belong to Secure Boot
> thunderbolt 0000:1c:00.0: probe with driver thunderbolt failed with error -110
try boltctl list to see if there is a physical thunderbolt
bluetoothd[760]: Failed to set mode: Failed (0x03)
try
journalctl --no-pager -o short-iso-precise 2>&1 | grep “Failed to set mode”
So from all error listed in your snippet only usb (and bolt maybe) deserves attention.
Now to your request, I’d do the following(I prefer to see the errors though) :
quiet splash loglevel=3 rd.udev.log_priority=3 vt.global_cursor_default=0
regenerate Grub
sudo grub-mkconfig -o /boot/grub/grub.cfg
Ensure plymouth is installed and set as default theme
If quiet doesn’t work you could pass a system.d line to the kernel, but it shouldn’t be necessary.
Moderator Edit: Merged consecutive replies
I too have the bluetooth error
bluetoothd[760]: Failed to set mode: Failed (0x03)
but I also have it turned off in System Settings. I can’t find it in my bios so I just ignore it.
The thing is, he can’t solve the errors by himself. Pretty much everything (thunderbolt i don’t know, that is to be investigated) is driver/firmware/kernel related - one can only wait for new versions.
I think he said he wants to solve them, just doesn’t want to see them parading at boot time. But then how would you know there is an error, unless you check the logs at every boot which for my taste it’s a tad tedious.
[koboldx@koboldx-x870e ~]$ boltctl list
[koboldx@koboldx-x870e ~]$ boltctl
There is no output
Any more ideas around the Thunderbolt device?
You total missed the point, i only want to ignore that warnings because the info’s are unfixable.
I also wrote multiple times that i don’t want to use a boot logo (i also wrote that i manually disable Plymouth, why should i want to enable it again?) and i also rejected the idea about quiet (dark blank boot)… everything was mentionend already in this topic.
When i understand the info’s correct, then Thunderbolt is the only option which maybe can be solved here.
Bluetooth warnings are temporary till i can disable it in Bios with the newest update.
Maybe that will be the solution for thunderbolt too - to disable it in bios. But beware, on some machines it is combined with some usb ports.
For the by-passers, for educational purposes, the loglevels explained. Although the article is for the kernel, udev, systemd etc. Settings all follow this logic, as in the example of @pwx above where he silences everything passing 0 as option everywhere.
Sadly this option not exist on my AM5 Mainboard Bios. But isn’t Thunderbolt from Intel anyways?