Found the issue; it doesn't like display arguments once set.

The unity3d folder is created/populated properly I think. I can see the Player.log and (indeed XML) prefs files (I can post the contents if you want). I did a chmod 777 -R on the unity3d dir and it made no difference. I tried running the program as root (xhost +) and it also didn't save or recall settings. I also disconnected an external keyboard with a built-in trackpad controller, but this also didn't change the behaviour.

I then tried running it from cli with different arguments and that's when I noticed a difference. Initially I made a program shortcut in KDE to always load with '-screen-fullscreen 0 -screen-width 800 -screen-height 600 -force-opengl'. I'm running it on a 12 year old laptop (core Duo, 4GB, Mobile Intel Graphics Media Accelerator 4500MHD, DirectX 10 capable) and at 1080p it is just too sluggish. So I kept the screen settings in there every time I load up the program. I think that's when things are getting corrupted or reset.

The fix for me was to run the program once with the preferred display arguments and I then save my user prefs and camera settings. After that I never start the program again with the above display resolution settings anymore; it just loads it back up from the prefs files; even the LOS/onboard camera settings, blur, etc.. I do still need to always add the -force-opengl argument. I've updated the KDE program shortcut link and it's now loading up every time with my controller already calibrated and the user profile settings loaded. Yaay! The external keyboard/trackpad also doesn't interfere with anything, so all good there too.

I do notice when running the program from cli it always exits with a segfault. This is at the very end after I hit the X (close) button from the main screen. It's probably some garbage collection or memory housekeeping/ gone astray but it doesn't affect the workings of the program.

I'm very happy with this sim as I consider myself still a beginner fpv enthusiast and I really like the lightweight program and bare bones training maps. They don't distract from learning to be in control over your aircraft. I also appreciate that it runs on modest graphics cards as I have stopped using dedicated game-optimised PC boxes around the time of Quake (anyone remember Voodoo2 cards?).

Cheers