There is some problem in http://…/foris/config/main/storage_plugin/
I was unable to perform btrfs format because the “Format & Set” button was grey and inactive.
I tried umout, manual format to btrfs, stop services accessing disk, tried SSD, flashdisk, every media type possible, clear browser cache, reboots… but nothing helped.
Finally I had to change button class type to “enabled” from “disabled”.
Then after reboot is the button blue and working, disk was successfuly mounted to /srv.
Hope it might help to somebody.
edit:
It seems that to activate format button is enough to to hit one of radio buttons directly. So line selector works and radio button is selected but it has no impact to activate format button. That’s what confused me. Anyway it can be improved so panic users like me can save one afternoon 