Librera in portrait (flipped)

Nerd help with Librera.

I use Librera to read on my phone, and it would be nice to have the screen in portrait mode, with the screen upside down, to read while charging the phone.

I found the option in the configuration menu, but it just doesn't seem to work on my Samsung Galaxy A36 phone...

I've tried restarting the app, and turning the screen rotation on the phone, but nothing seems to work.

All the other options (landscape and landscape flipped) works just fine. Even the "auto" mode work fine, changing in between all the other options but the one 8 want (portrait flipped)...

Not sure if this is a problem with the app or is some kind d of restriction with the phone.