Hmm I had quite the same problem.
I had to install another file manager.
I'm using a file manager called "Amaze".
It's from Fdroid. (no ads and very comfy once you get used to it).
That file manager lets me choose how to open my files.
So I just have a .love file in my device -> "open with",
I scroll all the apps and I choose "Love".
I think it's about the app's manifest but I'm not sure since I'm not an Android dev.
It seems that you can't force an app to open a specific type of file.
So one would have to edit Love's manifest and recompile the app.