I think the point you make about walled gardens needs to be addressed more than it is. It seems to have become normalized across all platforms and that is disturbing.
I fundamentally disagree with the premise of a walled garden when there are no other options to install on a device.
The web is the only freedom devs have left and even that is starting to erode - article 13, neutrality etc.
To be honest, the last freedom of small portable devices are the Pi and the NVidia cards and a build your own solution. While I understand this isn't a true replacement for a mobile, as it doesn't have access to the web everywhere, I can't seem to think of an independent alternative that hasn't been hobbled quite a bit.... plus they're pretty fun to build. You can build pretty neat ones the size of a DS that do what you want, but again, it's not a true replacement for what you're looking for. It is a hacked solution in the truest sense. =[
I fundamentally disagree with the premise of a walled garden when there are no other options to install on a device.
The web is the only freedom devs have left and even that is starting to erode - article 13, neutrality etc.