Hi, does LE apply any sort of restriction to requestors from given countries (namely Russia, Belarus, Syria...)? I am not referring to given extensions of the domains, but on requestors (such as public entities or Companies from those countries). How is it performed? Thanks
Let's Encrypt won't/can't issue to entities on the US "Specially Designated Nationals list". That's about it for "political"-type reasons that I'm aware of, though there are other restrictions for high-value/high-popularity domains that they have blocked unless the owner specifically talks to them about it.
There is also a rule that governments of particular sanctioned countries can't get Let's Encrypt certificates.
(That's different from the SDN list.)
Adding to what @petercooperjr and @schoen said above:
IIRC, LetsEncrypt - and many other technology providers - use a third party service to match domains/accounts against the sanctioned lists mentioned above. Those services have resulted in both false positives and false negatives in the past.