I do wonder if there is a market for a preinstalled self hosting computer or setup where the service would be automated backups, e2e encrypted of course, and perhaps high availability

Security updates.

And fixing things when they eventually break.

Honestly, there is a reason I still use a dreamhost shared plan. It's dirt cheap, been running forever, and I've never had to do the boring stuff.

And if they break my app, I can ask them to fix it.

If you deploy your app on a PaaS you still have to update everything inside the container.

Old school php hosting on a shared server does have some upsides - namely affordable support. (Sure, if I'm an extreme edge case support will not do much for me).

The same kind of thing for "self-hosting" would be cool.

Synology and likely other NAS vendors are basically doing this. A buddy of mine isn't any kind of Linux sysadmin but he's running his whole home media management setup as Docker containers on a Synology NAS. I assume they have off-site backup services available, too.