Looks increasingly unlikely that there will be convenient ways to have the best of both those worlds in a single device. For now it is somewhat possible with Android, but the experience keeps getting worse.
Maybe 2 phones are the way forward.
Maybe a PAYG phone which stays at home on my network for particular needs like banking.
Then a standard phone which is essentially a GNU/Linux distro.... mmm... Emacs on my phone sounds lovely!
Or will that munch your battery?
And I also carry a super cool small laptop that can tether to the phone and actually do stuff with.
One is an appliance, the other is a computer.
Used to have two phones ~10 years ago. A Jolla Phone was my primary phone with a sim card and ran most non-Google apps. Then I carried around a cheap Motorola Android phone that had no sim card but could run Google Play apps and when it needed wifi I shared that from the Jolla and otherwise it was fully offline and most of the time turned off.
So the phone that was closer to a small laptop was the one I actually used as a phone. Not sure if that is the setup I would go for again or if I would do it the other way around with the Google phone being the phone. If I do the latter I guess something like a very small Linux netbook would work as a second device, it such a thing exists.
I must admit, I don't do banking on the phone and keep all sensitive data off my mobiles.
If you're only doing banking at home, why would you do it on such a tiny little device?
Meanwhile, you can use it in termux if you are on android right now.