This is probably simple, but I thought I would post it in case someone else missed it like I did. For the longest time, I could not figure out how to copy and paste from the keyboard into an SSH session.
I figured out pretty quickly that I could use the menu on the toolbar to copy and paste:
The keyboard is the part that I couldn’t figure out at first.
In the perferences, you can find that the Remmina terminal has two options for copy and paste, but you have to use the Host key. By default, they are Host + C and Host + P.
My problem was that I didn’t know what the Host key was. I felt quite silly when I found that it was a preference on the Keyboard tab! By default, it is the right control key.