Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
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.
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
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
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.
APKMirror - Android Market and APK Downloads