It was getting hung up on my username and password, I believe - I have them as part of my bookmark URL and the new config file didn't have them, initially. I added them to the config and it didn't like that. I took them out of both and things seem to be in good order.

Hmm, that is weird.

Do you mean that you had something like https://selfoss.example.com/?user=davimack&password=CorrectHorseBatteryStaple as the bookmark? Or was there some other path? When I try this on my server, I just get redirected to /sign/in

Do you have selfoss installed in a subdirectory rather than a subdomain? That is not as well tested so I might have introduced a bug.

Could you please share your config (with sensitive fields censored), the precise version of selfoss and the web server?