ill tell ya, i really would absolutely love to put your game onto PortMaster. But there's something going on with your game i haven't run into yet. my friend who could maybe do something with your source code is busy right now and doesn't have much time to look into it. looking at your game in 3,1 engine, things seem a bit different that's for sure. I opened the engine and said i was missing dependencies and had an option to "fix dependencies" on LogoScreen. But i couldn't understand what it was meaning. But i have purchased your game, not only on Steam, but here as well. so if you can somehow go through your PCK, and remove anything and EVERYTHING that has to do with steam, i can probably get it to run. that way i can make a patch that when people buy your game and move the original pck into the folder, the patch will remove everything that was edited out in the pck you give me and will allow it to run on these Linux handhelds. its just a little out of my wheelhouse the way you put this game together, and i'm at a bit of a loss on what i would have to do. maybe even try to simplify the game as much as possible, and make the structure close to something like a GoDot game "Blood-X-Thirsty" form Steam. That game worked right out of download, no issues whatsoever. drag and drop. I often have to edit a few things with input mapping, or change res:// to user:// in gdscript or other small changes. But with yours, i just don't know what is going on. haha.
if you wanna take a little bit of time to help me, help you, get this new pck created and exported, having your game on PortMaster exposes it to a TON of people who will see the game and will have to buy your game to play it. But the ability to play it on their Linux handhelds is a driving force for purchasing games you otherwise never would have even known about, let alone purchased. So, get back to me. my email is unusual.paladin@gmail.com if you want to send me a pck you think might work. I've had many many devs send me edited game files to allow their game to work on PortMaster and hopefully, we can get your on there too with a little luck!!!
Or maybve it would be as simple as you taking your games resources, adding them to a normal Godot 3.1 Engine, and exporting it. Although, that seems like something that might not even be possible. but if it is, that would probably fix most if not all the issues. Your game is so cool man, id love to see it working!