F-Droid - F-Droid is an interesting alternative for Android users who want to try something different and not have to use the Goole Play store all the time.
AppSales - Find the best Android apps and games from Google Play that are currently discounted or free for a limited time
Aptoide - Aptoide is a third party replacement for the traditional Google Play Store.
AppRecs - AppRecs sorts through reviews in the App Store and automatically helps you filter out inauthentic results.
APK Pure - Download apk for Android with APKPure APK downloader. NoAds, Faster apk downloads and apk file update speed. Best of all, it's free
TheAppStore.org - Find apps by rating, price, category, updated date and more