Hi!

I just did several upgrades & migrations... 2 x stretch->buster->bullseye last week, then 2 x bullseye->chimaera :
I saw the same problem after

apt-get install eudev

init and sysvinit-core removed just before rebooting without init ...

As my wheezy NAS was systemd-free, no problem there after wheezy->jessie, direct migration to beowulf,
and beowulf->chimaera, a piece of cake