Ideally you want something that gracefully degrades.

So, my media library is hosted by Plex/Jellyfin and a bunch of complex firewall and reverse proxy stuff... And it's replicated using Syncthing. But at the end of the day it's on an external HDD that they can plug into a regular old laptop and browse on pretty much any OS.

Same story for old family photos (Photoprism, indexing a directory tree on a Synology NAS) and regular files (mostly just direct SMB mounts on the same NAS).

Backups are a bit more complex, but I also have fairly detailed disaster recovery plans that explain how to decrypt/restore backups and access admin functions, if I'm not available (in the grim scenario, dead - but also maybe just overseas or otherwise indisposed) when something bad happens.

Aside from that, I always make sure that all of all the selfhosting stuff in my family home is entirely separate from the network infra. No DNS, DHCP or anything else ever runs on my hosting infra.