Is flathub.org not a great GUI for browsing apps. If you click the down arrow next to 'Install', it gives you the command to install from the command line, so it's just a quick copy and paste.

Or you can download the .flatpakref and define your own app handler instead of gnome-software. The handler just has to run `flatpak install /path/to/app.flatpakref`. A quick bash script + something like zenity (for gui dialogs) could take care of that.

A TUI would be a good addition?