After reformatting my USB-stick it became unreadable by Android filesystem. Android Supports only NTFS or FAT32, but whenever I try to format USB-drive from Ubuntu to any of the types I can see flag "msftdata" in GParted. I believe this is the problem. Windows and Ubuntu can read it fine though. Ubuntu filesystem seems to struggle to determine USB-stick's filesystem, but can read it. I tried to reformat into different types, change flags, but no success so far.
UPDI was able to read USB-stick using StickMount app from Play Store. I would still prefer Android to mount it though.