Several hours later, the little #PeerTube instance that could is now in a much healthier place. I just had to migrate the entire thing manually, because old versions of Ubuntu have no viable upgrade path.
At least a do-over means that the server is set to whatever defaults were intended for the latest versions of things.
RE: https://social.wedistribute.org/objects/de34bf6b-2d0f-4d19-b35f-7ae496458562