F-droid often has nice apps, but too often, they are just not good enough for what I want or need[1]. In that case, I'll gladly pay on the play-store because the paid version is nearly always (but certainly not guaranteed to) have less or no trackers ads, and malware included. The free apps far too often do.

I use https://exodus-privacy.eu.org/ to check for trackers, ads and "malware".

[1] Far too often, the apps there are "OK, but...", clearly the work of a someone building a quick "works for me" or someone learning how to build apps. For some tasks, "just OK" is good enough. More often it just isn't.