Is it just drag'n'drop to "ports" and the sh file to "ROMS/Ports", on muOS?
That should do it (https://muos.dev/installation/portmaster#download-the-portmaster-port-files). You'll also need to install all the runtimes via the PortMaster app (muOs > Apps > PortMaster > Options > Runtime Manager > Download All), as you're manually loading here (as opposed to installing via the app, which would download the dependencies automatically). Of course: don't forget to add your game files (as per the JSON "inst"). Don't worry about the meta files for now (gameinfo.xml, port.json, README.md, screenshot.png) -- that's for the catalogue packaging.
How do you use the menus on devices without the joystick?
You can tap the power button quickly to swap the D-pad to Analogue mode (https://muos.dev/#handy-hotkeys)
And if you get to putting these in the catalog eventually, please link to my own website: ottoojala.com, instead of itch, in the credits - I might leave this platform at some time.
Will change it right now, so it'll be ready whenever we release :) -- just let me know when you're ready, and whether or not to include the game files (or have users download and manually add these).