The Firefox "hamburger menu" (3 horiz lines top right) has 3 icons under the zoom controls for cut, copy and paste.
Also you can switch to the Terminal Keyboard (via globe key menu) and use CTRL C, CTRL X or CTRL V.
EDIT:
I'm not 100% sure about this one but I think Firefox also has an option to automatically copy selected text.
I must have dreamed up that option . After a look through the settings I can't seem to find it.
Cheers!
Also you can switch to the Terminal Keyboard (via globe key menu) and use CTRL C, CTRL X or CTRL V.
EDIT:
I'm not 100% sure about this one but I think Firefox also has an option to automatically copy selected text.
I must have dreamed up that option . After a look through the settings I can't seem to find it.
Cheers!