GUI-Support to mount LUKS encrypted Volumes

Not much to add to the title.
Atm there seems to be no support at all to mount (LUKS) encrypted volumes using SSH/CLI let alone over the GUI atleast ootb.

Would be great to have atleast a easy way to do it over ssh if possible or even a seperate Menu item in Kodi Settings.

This is quite a niche request. Unfortunately, such features with little demand (very few ppl expect encryption for a simple media player device) are destined to the bottom of the list. You are absolutely welcome to submit a PR to the OSMC github though.