A few weeks ago I checked XDA Labs, which is an alternative app store / forum browser for "indie" android apps. XDA Developers is the best place to find out how to root your phone, install a custom ROM, check out amazing applications by talented developers, etc. But this time, I found an app that caused my phone to slow down so badly I didn't know what was going on...
...until I opened OS Monitor (which requires root on Android 7.0 and above), which you can find on F-Droid. In the main tab it shows you the percentage of CPU an app is consuming. And smack dab on the top of the list was:
Shame on CoinHive for making it possible for people to (excuse my French) r*pe the f*ck out of someones computer resources, and shame on devs for thinking it's a good idea to include it in a mobile app.
So yeah, if somethings up with your phone and it's slowing down, open up OS Monitor and see what's up.
~This has been a rant~