I noticed my apk went from around 300kb to 1.9mb only by adding firebase ads library.
I saw another post mentioning that you can exclude certain classes (Google classes) and that only made a few kb difference. That was for b4a 6, so perhaps b4a since then does this sort of optimization automatically?
Anyway, if that's the price for me to pay for firebase ads then so be it, but I just wanted to make sure I wasn't missing something.
Edit: I was following the instructions on the post about integrating the firebase library into a project. I'm on my phone right now so I can't easily post links.