You can use Yalp Store [1]. It allows to search and filter Google Play Store apps based on (i) Apps with ads, (ii) Paid apps and (iii) Apps using GSF.

Another reflex is to look on the F-Droid Store if an equivalent FOSS application exists before looking for one in the Google Play Store. There are some excellent apps there, such as NewPipe [2] for instance!

[1] https://github.com/yeriomin/YalpStore

[2] https://newpipe.schabi.org/