How can I install Xapk files on an Android?
Use a mobile file explorer to locate the downloaded XAPK and rename it to .zip.
Unzip in any folder.
Create a new folder in the local folder system of your device, namely /sdcard/storage/emulated/0/Android/obb/<OBBname>/, where <OBBname> is the OBB file name itself without the extension. That is, if the file is called myapp.developer.obb, the folder should be called myapp.developer.
Copy the OBB to the folder you just created.
Install the APK that was found in the XAPK as usual.