APKUpdater Finds Updates for Your Apps Without the Google Play Store
Android: For most users, the Google Play store is the best way to find apps and keep them updated. Whether you are using non-Google ROMs or downloading apps from other sources, APKUpdater will keep you up to date.
This app, made by user Rumboalla XDA, scans your app list and then finds updates for those apps on sites like APKMirror. It can also optionally scrub the Google Play Store itself to find app updates. However, it will not automatically install new versions. You will have to download and install them one at a time. However, it is still helpful to know when an update will be available.
This might not be necessary in most situations, but if your custom ROM doesn’t have Google Play or you’re avoiding it for privacy reasons, this is a handy way to fill in the blanks.
APKUpdater: Get updates for your apps without the app store! via XDA