I had the same problem.
If anyone else needs a fix for now, edit the docker container and change the repository to linuxserver/nextcloud:20.0.2-ls107, this has got my Nextcloud working again.
I had the same login problem. Been avoiding updating the container but my docker.img got corrupted so it pulled the latest version. Switched back to 3.10.5, login works perfectly. Rebooted the container again and it picked up all my cameras thankfully.