Just adding here for the sake of completeness that this particular error:
Failed: Path to plugin integration is null!
happens when you are missing submodules in ayon-unreal repo. You can either clone it with submodules using
git clone --recursive https://github.com/ynput/ayon-unreal.git
or when you already cloned it, just run:
git submodule update --init --recursive
the submodule is actually unreal integration plugin that is used if pre-existing plugin in Unreal Engine isn’t found (manually built or downloaded from FAB)