Protector is no joke at all. It's one of the leading engines and it's capable to beat monsters like Houdini 4. TCEC-8 is the proof!
Unfortunately, i could not rank the previous Android compile 1.8.0 for frequent bad termination issues. I hope that new compile heals the problem.
To use Protector under Droidfish, use the UCI engine directly and for Chess for Android, follow the uci2xb method explained previously.