I had UEFN installed yesterday but now it is gone. It failed to update and now it says it is no more supported anymore. I play Fortnite trough Amazon Luna and started development just this week. It is possible to use Unreal itself for creation of Islands instead. At least until the problems with UEFN are fixed.
No. Fortnite uses a distinct fork from regular UE. If UEFN isn’t working on Luna, try installing it from the Epic launcher.