I went with Gatorskins. They look and feel nicer than I was thinking, I really like the tread pattern, and there seems to be latex on the sidewalls.
I couldn't find anywhere on the packaging or the literature or the advertising whether they had latex or butyl tubes.
I've got them stretching on old clincher rims. Reassuringly tight fit, not insanely tight.
I've got a few more months on my Hell of the North sewups which have been great.
Usually when I find a tubular I really like, they stop making them before it's time to buy more.
- so I expect Conti will discontinue these for 2026.