Good luck. They tried to block it in Russia, but it simply broke their own internet for a while and the effectiveness was spotty until they gave up. To this day I believe there is quite little cooperation between the Russian government and Telegram, despite not being E2EE by default, if we don't consider conspiracy theories, unlike all the other services used in Russia which are basically all backdoored by the state…
If Russia TRULY wanted to block Telegram, then Mr. Durov, who accidentally operates from and resides in Russia, would have been kidnapped and tortured until Telegram goes down or he hands the keys over to KGB.
Since Durov is still alive and free... the conclusion is kind of obvious.