Welcome to the world of Linux...
I think you just need to add your login username to the group called 'dialout'.
Then it will work.
There is a graphic interface for this - but it's really easy to type a couple of lines in a terminal screen to make it happen.
open a terminal and run the following. (replace USERNAME with your username)
sudo usermod -a -G dialout USERNAME
(you will be asked for the password of the account who setup the Linux install - probably you - so put yours in)
(if alls well now type this)
id USERNAME
(press enter and it will list groups you are a member of, this should now include dialout
Importantly - now log out and back in again and it should work.
Hope this helps - It's the first job to do to a ham radio install.
If you want to check up on this first - you would be adding an already existing username to an already existing group.
ps finding a local Linux User Group might be a good idea, there's nothing like face to face support!
73 Dave H G0CER Shropshire linux Users Group
https://shropshirelug.wordpress.com/