In reply to the above question from the previous thread: yes, the issue is still relevant for systemd 252.1-1. I tried installing tpm2-abrmd and got infinite boot again with udev-based UKI. Probably an overlook from systemd devs, and also not severe since circumventing it is quite easy with removing of offensive package I had installed by mistake.
Can’t test systemd-based unified kernel image ATM because there is another issue with that – perhaps cryptsetup is to blame – manifested by failure to mount swap lvm partition – and, consequently, another infinite boot experience. Haven’t looked into that yet.