Hey OP ! I’m digging this back up, I found a smartphone that might interest you (with a few caveats) : The Nokia G42.
It’s an interesting one ! Built to be durable and reparable. It’s a smartphone, but Nokia worked with iFixIt to design this model; you can remove the back cover to “easily” change the battery, the USB-C port and the screen. It has a headphone jack (even if you don’t care), a decent screen (90Hz, 720p though), has expendable storage to 1To, approximately 2 days of battery life (Nokia claims 3 days), it’s “cheap” (can be found where I leave to around 230 euros) and has take decent photos (for its price). Not sure about rooting this one though !
The main issues from my point of view are updates (3 years of security update is OK, but 2 years of guaranteed Android updates is short), and the processor, which is quite weak. Not sure how it will perform in newer version of Android.