I see the 'battery backed' as an issue. Keeping it plugged in like that is going to harm the battery. That and the fact that my Xiaomi 12 runs USB 2.0 .... I'm stuck running stuff on MacBook at night when I don't use it because of that. Electronic price need to become reasonable again, a 8gb raspberry pi 5 is about 200€ right now. It's absolutely insane. My pi 4 did cost me 40€ a few years ago.
It's an old phone getting a second life, the health of the battery is probably not a big concern at this stage.
i'm thinking more about long term.