I had the issue of the sd card not mounting at all on my Poco F1. This has helped me. You can try it out. https://askubuntu.com/questions/95391/how-do-i-mount-an-sd-card

I have solved the issue. The fail was a media scanner corrupted database located in: /home/username/.cache/mediascanner-2.0/mediastore.db Once removed the file and rebooted the phone, new database was created succesfully. I left this topic because may be useful to other users with the same problem. Thanks to all the developers for keeping this project alive

@Teigneux glad to help