For your first topic the problem with formatting an flash drive to mkfs.ext4 is a known bug in the OS and under investigation. FAT32 should work normal.
Second the rights of mounting a drive was restricted because of security reasons in the version 1.8. This will be reworked in the next release milestone RM21.07 (version 1.10) coming up end of July.Thenit will be possible again also via a web based user interface.
At least please beware, that a standard (productive) ctrlX CORE will have no user with root rights. This access is for development purposes only.
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