I was going through a sample pack of paper, printing the same test pictures over and over (being very careful to use the right profile and driver settings for each particular sample sheet of paper). When I got something like this.
It wasn’t instantly obvious to me what the problem was. I tried another paper. I tried a nozzle check.
That wasn’t obviously bad. The black printing was weirdly faint, but this was maybe the second time ever I’d done a nozzle check on this printer and I didn’t remember the last one that well. (Of course, they look nearly identical to all the other Epson printers, so arguably I should have caught on sooner).
So I resorted to calling service. They said do a head cleaning anyway, so I did a head cleaning.
And got this nozzle check.
Well whaddya know! I’ve never had an entire color go out 100% suddenly like that.  And the arrangement of check squares was a better layout with the dark black missing.
The actual test print looks much better too.
So the new Epson 3880 is still my friend.