I couldn't find a straightforward way to clone Android apps, without watermarks and such, so I created clonemy.app to do just that.

Mods: XDA Ban Appeals Team confirmed this is not warez after removing a similar post & mistakenly banning me, please PM me if there any doubts.
Features
- Upload an APK file, choose a name, wait, download the cloned APK
- The clone APK has a new package name, which allows for installing the clone alongside the original
- Create as many clones as you want
- Run multiple different versions of an app alongside each other
Limitations
- XAPK files are currently not supported
- Cloning is a complicated process, and some apps are not supported
Technology
- Apps are decompiled, package name is changed, display name is changed, after which the app is recompiled and ready for download
- Cloning is created with Python, on top of Apktool and Android build tools
- The website is created with Starlette
Mods: XDA Ban Appeals Team confirmed this is not warez after removing a similar post & mistakenly banning me, please PM me if there any doubts.