Don’t think that’s an option really, the file manager is like the android version of the open file dialog in Windows now. Ever since they implimented secure app storage. Like op replied to you it’s mostly hard coded in the apps or something. It’s gonna get worse too, pretty sure android 12 made it so you can’t use a third party camera for pictures taken through other apps, and on my OP9 Pro you can’t select a alternative gallery app.
Same, I have the Amazon gts 2 and it’s alright but it’s not the same. Thinking of getting the PineTime next but the firmware was a bit underwhelming last I checked.