Copied from someone else reply, and it worked for me, even on non rooted phone (use es file explorer and grant acces to obb folder via uninstallation of file manager update) i can log into my old account
For anyone wondering, you can log in using your google account with a signed apk.
The method goes like this:
Launch the original game file.
Sign in to your google account and wait for the game to load up.
Exit the app.
Go to your file manager and in "Android/Data/" theres a file called "com.awesomepiece.castle", change the name to "com.awesomepiece.castlexx".
After that, go to "Android/obb/" theres a file called "com.awesomepiece.castle", change the name to "com.awesomepiece.castlexx".
After you finish changing the names of the 2 folders, you can uninstall the original game file.
Download the mod apk version of the game, before launching, change back the name of the 2 folders to "com.awesomepiece.castle".
Change storage permission of the apk to enabled, put the BlackMod.license inside "Android/obb/com.awesomepiece.castle".
Launch the game, when it asks for permission to enable over screen application enable it and close the app.
Launch it again and you'll be able to sign in to your google account!
original post :
@jajaj123