Thank you for the method of avoiding this problem with a flash drive installation. If I refuse the Manjaro update of mkinitcpio from 34-1.1 to 35.2-2, I can update my system and reboot it without seeing the dreaded “can’t find UUID” message.
Just for interest, I did a fresh installation of Manjaro to my flash drive and saw that the mkinitcpio version was 34-1.1. I then updated this new installation, including mkinitcpio to 35.2-2, and to my amazement I could reboot the system without any problems. So it seems that there is something in my old installation which is incompatible with 35.2-2, which makes me doubt that any “fix” for mkinitcpio can be hoped for.
it’s already fixed. the problem was they removed something called resolve_device because they didn’t know our use case still needed it so now they’ve added it back so now we only have to wait for the next update. the success of your new installation does not mean previous installations are unfixable.