To run desktop programs on the phone, it is not enough to install a flatpack. Without a suitable window manager (e.g. Phosh) with scaling options, the result will be poor. See also “mobian”:
https://wiki.mobian-project.org/doku.php?id=apps
Tested programs that can be started, but are hardly usable due to various errors (display doesn’t fit, objects cannot be clicked, keyboard can’t be used…). Right now it’s just a dream to run desktop programs on a phone without changing any code. Flatpacks weren’t made for that either. Don’t expect miracles.
I don’t want to take away any illusions, but these are exactly the problems that even “real” Linux phones have to struggle with. Without code adaptation against a mobile framework, there is no reasonable result.
It’s a long way home 