@opiumfor, you could try to use some kind of foreign DNS lookup service (including a web-based one or an ISP looking glass server) to look up
ocsp.int-x3.letsencrypt.org from another country, and then set an
/etc/hosts record to point to the resulting IP address. As this is a CDN-backed service, the CDN (in this case Akamai) is generally willing to connect you to the appropriate service even if you use an IP address that is not the usual or intended one for your country.
As of right now, some IP addresses in the United States for this host are
I believe Akamai will connect you with the appropriate Let’s Encrypt OCSP service if you connect to
ocsp.int-x3.letsencrypt.org at any of those IP addresses.