I think it was the 2nd gen that had the awful touch strip (if you haven't seen it, think of it as a shitty implementation of the touch bar). I have the 5th gen (2017) and it's a fantastic machine that works really well with Linux. The 6th gen had some issues with Linux, however, those were mostly Intel's fault iirc.
My memory is lousy. You are most probably right about the generation, or somewhere near. If I had a 1st gen, I certainly skipped at least one generation, so I'd put it at least 3rd generation. Not as late as 5th though.
