Comment by schoen
Yep, they started in 2020: https://letsencrypt.org/2020/02/19/multi-perspective-validat...
This has been challenging for some subscribers who are unaccustomed to receiving any legitimate site traffic from foreign countries.
https://community.letsencrypt.org/t/multi-perspective-valida...
Now that it's a requirement for the whole web PKI, it will be interesting to see the pressure against blanket geoblocking increase. (Or maybe more web hosts will make it easier to use DNS challenge methods to get certificates.)
Geoblocking is one of the most drastically effective ways someone can reduce their attack surface. I'd give up encrypting traffic entirely before I'd give up geoblocking.