Currently the best Google Play Store alternative is to use F-Droid. As explained on the official site, F-Droid is an installable catalog of
FOSS (Free and Open Source Software) applications for the Android platform.
See the F-Droid website or the official GitHub page for more info. Other alternatives to the Google Play Store include:
Aptoide – An independent marketplace for Android apps. Be aware that Aptoide suffered a major hack in 2021, exposing more than 20,000,000 accounts. You’ll have to decide for yourself whether you are willing to use this service.
APKMirror – This is a large library of APK files uploaded by different users (be careful).
Aurora Store – A fork of the Yalp Store.