I think this is a good starting point:

nostr:naddr1qq9hyetvv9uj6um9w36hqq3qgcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqxpqqqp65wjvcq4q

Easiest way to run a personal "backup" relay is umbrel in my opinion.

Of course you can use my relay nostr.kolbers.de too. But It could be that there will be a small fee in the future as a protection from bots.