Is there an overview somewhere of stable third parties that do these builds? I might want to use one of them and didn't know this was a thing. Not having access to my own data is the only reason I haven't installed the OS yet

The problem is that even if you build this yourself, and sign it with your keys, the signature of the builds will not lead to positive hardware attestation. This, as noted by @palata, is required for passing Play Integrity Checks, and in turn is the requirement for using banking, tap2pay & co.

It's really a bummer that Google probably won't certify pre-rooted devices. It would obviously only do harm to them and not fit into the scheme of our big tech companies pushing anti-circumvention laws, but some high-spirited side inside of me still has hope.