Pushlink - Android Enterprise Mobility Management made simple
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.
AppBlade - AppBlade provides essential tools for mobile app development.
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
WSO2 API Manager - WSO2 API Manager is a 100% open source enterprise-class solution that supports API publishing, lifecycle management, application development, access control, rate limiting and analytics in one cleanly integrated system.
APKMirror - Android Market and APK Downloads