Developed on Arch Linux, previously Fedora.
I kinda hope someone makes a Gambas 3 Flatpak.
If it is because your packaged runtime is out of date, try launching from the IDE (if installed). I find that skips the version check, even if older than what I used.
Worst comes to worst I will upload a build on an older Gambas from another machine I have.
Thanks for trying it guys.