This has been a serious concern of mine. In the event that I prematurely die I have everything set up with automatic updates, so that hopefully my family can continue to use the self-hosted services without me.
Nextcloud will not stop shitting the bed. I'd give it a few months at most if I died, at which point my family would likely turn back to Google Drive.
I'm looking for a more reliable alternative, even if it's not as feature-rich.
I've told my wife and family that if something happens to me, they need to start migrating all their stuff off my self-hosted services to cloud services because its a matter of time before something fails and nobody's around who knows or cares to fix it.
If you're ok with just file storage sftpgo has been solid for me for years now. Does sftp ftp and WebDAV (like nextcloud). Webui isn't as pretty but it's fast. Mobile apps will be various sync apps with sftp or WebDAV support. On Android folder sync pro is pretty good for keeping documents and pictures backed up
The way that they do updates doesn't make automated updates very easy. There are usually a few little nagging things that have to be done or changed and they don't always seem to be the same. I just update manually and make sure I've got a good backup of all my family's files.