Not everything here will be for everyone and there's obviously a _lot_ more good stuff there, but here's a list of some good apps to look at:
- OsmAnd - offline version of Google Maps
- FreeOTP+ - FOSS 2FA app
- NewPipe and/or SkyTube - Youtube app alternatives. They break every so often when Google changes something, but when they work, the experience is much better than the stock YouTube app
Some of these are available from the Play store as well of course, but not all. For random utilities where I want something lightweight that does a basic task it's the first place I go. Ironically it's some of these fdroid apps that are what keep me on Android. I'd love to be rid of Google, but would really miss AntennaePod and NewPipe.
https://f-droid.org/
As others have mentioned, Aurora Droid and Aurora Store are helpful alternatives to the Google app store.
https://gitlab.com/AuroraOSS/auroradroid
https://gitlab.com/AuroraOSS/AuroraStore