Probably your ISP, or more precisely, the ТСПУ box they were required to install. You can use this tool to test your connectivity to these hosting providers that the government dislikes: https://hyperion-cs.github.io/dpi-checkers/ru/tcp-16-20/

Ken himself did block access to his website from Russia for a while after 24/02/2022, but right now it loads for me after a CF captcha.