It's not QB64.
Unlike Windows, *nix systems do not start searching from the program directory by default.
On Linux, if the path "TankDrum\img\tankdrum.ico" is within the current directory then you need to tell that to the OS: "./TankDrum\img\tankdrum.ico".
If you want full cross-system portability you can do that in Windows as well. There's no harm in it.
Unlike Windows, *nix systems do not start searching from the program directory by default.
On Linux, if the path "TankDrum\img\tankdrum.ico" is within the current directory then you need to tell that to the OS: "./TankDrum\img\tankdrum.ico".
If you want full cross-system portability you can do that in Windows as well. There's no harm in it.