Only one partition cannot be unmounted (on other drive than the one the system is installed on) . It is also the only ext4 partition on that drive, the other two are ntfs.
I am using dual boot, have rebooted to fully shut down Windows, all partitions other than the system-running one are unmounted.
In Dolphin it says some app is using the partition
which one could that be? (Dropbox and such are shut too)
lsof | grep /media/cip/DEPO
will tell you – Rinzwind Nov 29 '21 at 15:09