I apologize for the delay, but I’ve got a bit of work to catch up on.
I end up in setting up a fresh installation on my private laptop. Afterwards, I compare the mkinitcpio.conf from the fresh installation and from my broken business laptop.
And an interesting difference appears at the HOOKS line:
Fresh installation
HOOKS=(base udev autodetect microcode kms modconf block keyboard keymap consolefont plymouth encrypt filesystems)
Broken one
HOOKS=(base systemd autodetect microcode modconf kms keyboard sd-vconsole block sd-encrypt filesystems fsck)
So I changed the line from the broken one to the fresh installation, fired mkinitcpio -P, update-grub and reboot. And everything is working 
The pacman.log ends on both laptops, exactly with the line (of course with different timestamp):
[2026-05-27XXX] [ALPM] running 'pacnew-checker.hook'...
If I had to guess, I’d say the pacnew-checker crashed in the background, which is why the line didn’t make it into mkinitcpio.conf as it should have.
It’s also possible I simply closed it mistakenly. It was only during the second run on the second private laptop that I was absolutely certain no pacnew-check process was shown to me… In both cases, I updated with the pamac-gui not in shell.
I don’t know if that makes sense, but everything’s working again now. 