Um, I actually didn’t think of that… I think I need to be a subscriber to do that, I’m happy to do that and have just been test-driving before I signed up, I’m pretty happy with Ardour tho (this one issue notwithstanding) so yes maybe I should get on with that, might solve this problem!
UPDATE: I am now a subscriber (yaay) and my initial testing suggests that yes this has solved my problem (my current episode opened up and has mic input no problem). Feeling slightly foolish that I didn’t think of this before, in my defense I did run a system update at some point in the troubleshooting process…didn’t think of the fact that the Linux Mint software center version was still 5…
So, tentatively, all is well now - thanks for the help!