i see that the userdata dir has root/root rights.
root@DietPi:/mnt# ls -ltr
total 28
drwxr-xr-x 2 root root 0 Feb 14 2019 b819bea4-0b7f-4903-9669-244b0f5d6720
drwxr-xr-x 2 root root 4096 Jul 14 20:24 nfs_client
drwxr-xr-x 2 root root 4096 Jul 14 20:24 ftp_client
lrwxrwxrwx 1 root root 37 Nov 24 16:44 dietpi_userdata → /mnt/76D062D4D0629A5F/dietpi_userdata
drwxrwxrwx 1 root root 20480 Nov 24 21:49 76D062D4D0629A5F
root@DietPi:/mnt#
Edit: internal dir(/opt/Radarr) seems to work ok! I can see its files in smb client in android.
any ideas for the external /mnt directory?