NetworkManager seems to operate correctly without systemd, although maybe there is some aspect of it that I’m not using that does require it. It’s working find on both desktop machines and laptops though, correctly managing ethernet, wifi, and vpn connections.

Likewise, I’ve not encountered any issues with cgroupsv2.

Support for different init systems was improved in Bullseye, although sysvinit had pretty good support even before then. I followed the instructions here and everything seemed to work out of the box.