Sorry for late reply.
I managed to install using djircfcc.com hack. It’s an fcc hack that grants you install permissions if you have adb appcontrol who open while applying the patch.
Then, download Amazon appstore. Managed to get litchi installed but that’s it. It didn’t find the mini 3 pro as it’s not supported in that version of litchi.
Hell, I even managed to install plex for fun. It actually worked.