Short video where he goes over a couple important things
- Add an icon to your game
- Add a splash screen
- Set the main scene of your project properly
- Add your game name in the project settings + localizations
- Make fullscreen the default (most of the time)
- Add a custom mouse cursor
- Enable AA if applicable to get rid of jaggies
Theres a page in the docs that talks about getting the icon up https://docs.godotengine.org/en/stable/tutorials/export/changing_application_icon_for_windows.html . Gimp should be available on Linux