When I attempt to build the game with IL2CPP, the Editor tells me “currently selected scripting backend (IL2CPP) is not installed”. Even tho it is, according to both Unity Hub and my file system.
Which platform are you targeting?
Windows
Does this file exist in your Unity Installation?
\Data\PlaybackEngines\windowsstandalonesupport\Variations\win64_development_il2cpp\UnityPlayer.dll
That’s how Unity determines whether it is installed.