So if you are looking for just personal backup rather than hosting a public relay for everyone, its actually quite simple to setup. I have a raspberry pi running umbrel and it has a locally hosted relay that i connect to one of my npubs. You also should try nostrsync.live and run a DeepSync which will go into a whole bunch of relays and pull old data. Some relays make copies of others so there is a good chance that running that will pull up your old stuff. Let me know how it goes.