OpenBSD's support should be pretty close to parity with Asahi as far as what hardware is supported. One of the developers on Asahi is an OpenBSD dev. I would advise looking at the release notes for OpenBSD starting from 7.0 or 6.9, it has pretty good sections on what is supported. NetBSD, there are instructions buried somewhere on the NetBSD website on booting NetBSD on the M1, but I have not seen much else (perhaps more info buried in the mailing lists).
Right now, it looks like of all the BSDs, OpenBSD is rather leading the way on this.