There was a propriety implementation a few years ago (written in Rust of all things), but I think it's dead.
I think the bigger problem is that both iOS and Android are doing everything they can to deprecate the concept of a filesystem. Android has a history of killing filesystem features, receiving tons of developer backlash, and then hacking in workarounds with reduced performance. I think the writing is on the wall.
In my experience, porting general purpose tools to Android is a nightmare.
Hopefully something like pinephone gets good enough before things are too bad.
As long as Android has a Linux kernel running in the background there will be filesystem access. If Google ends up switching to Fuchsia this might change but we're not there yet. General purpose tools seem to run just fine on Android for the most without the need for much porting as can be seen by glancing through the list of patches [1] needed to build a host of packages for Termux.
Not trying to come across as argumentative, but have you personally worked on porting something to Android? Termux actually illustrates my point. That situation is an absolute mess[0].
Yes, I ported a few tools to Android and worked on a few Android ports to random devices (Motorola Defy and Ainol Novo Advanced 8 being the ones I was most involved in). With regard to the problems of the "Play store" requiring $things I'm not affected since I do not use it, there is no Google-proprietary software on any of my devices. If I ever need something from the store I get it anonymously through Aurora Store. Maybe this is why my opinion of/experience with porting *nix tools is less negative?
I think the bigger problem is that both iOS and Android are doing everything they can to deprecate the concept of a filesystem. Android has a history of killing filesystem features, receiving tons of developer backlash, and then hacking in workarounds with reduced performance. I think the writing is on the wall.
In my experience, porting general purpose tools to Android is a nightmare.
Hopefully something like pinephone gets good enough before things are too bad.