As I see it there's a few missing features, and they need to be solved anyway to make self hosting less painful in general, right now I don't see many good ways to do it at all unless you like stuff that unpredictabily needs maintenance.

Play store needs to be split into provider and interface APIs, so you can add your own repos and still have it work with existing tools.

Remote management needs to be a thing for sure, installing apps is the hard part of that. WearOS does it amazingly, just connected to BT and the host play store does it, but you'd need the split app store to make that work well with open source third party repos.

Automatic updates would be solved by that, just deploy your app on a repo, and update via the play store or your interface app of choice.

Finally you'd have to solve the biggest problem with ANY self hosting as far as I'm concerned, how to handle certs and domains with zero manual IT work(Has to be truly zero, no chance it needs maintenance while you're on vacation).

I've been saying this for a while, we need pubkey-based domains like .onion URLs, but without the onion routing, so there's no dependence on a CA or anything that might be hard to do in a fully automated "Scan the QR and connect" context.

Or, more likely, Google gives you a service.yoursubdomain.google when you buy Google One, and routes stuff ngrok style for you, with lots of spying, because P2P hasn't been their thing so far. Perhaps one of the forks could do it though.

Without eliminating domains and certs, I'll continue mostly ignoring self hosting, I don't want any chance it goes wrong while I'm too busy to fix it, since there's no dedicated support staff, just me.

It would also solve the other half of remote admin, apps could just declare a web interface for admin that you access if you have the secret URL.

Then you'd need some systemd alternative to manage processes. You'd have to be able to say "Start this on boot, restart it on failure, and never clear it out of RAM".

On the hardware side, phones are already close to perfect. Keep the screen and NFC and Bluetooth, for QR based connections and the like, keep the battery as a UPS, but add more USB ports, Thread/Matter, and ditch or downgrade the cameras.

The filesystem probably needs to support snapshots, and Android should get a Full Backup and Restore Provider API to make it easier to back up everything, just the home folder, just one app, just the settings, just the data, etc, to your chosen provider, maybe even with hooks for apps to respond to import and export, so that the state of your app is totally portable and needs only a few clicks to restore from auto backup.

Finally, we need a cpanel-like VPS management tool to migrate your stuff to cloud hosted if you want, that can take backup files, and show you what's on the remote device's virtual screen(Again, so QR stuff works) or at least what's being displayed via some "Admin screen API" if you don't want to drag the full graphics API into it(But keeping graphics all the time seems like a good plan for standardization, and for kiosk type stuff).

And then finally, you'd probably want a some of the features from a normal-ish Linux userland, or as close as you could get, to make porting existing stuff easier, but even without that, I'd say the porting would be worth it.