For those affected by the blocks, Signal recommends turning on its censorship circumvention feature.
Signal is being blocked in Venezuela and Russia. The app is a popular choice for encrypted messaging and people trying to avoid government censorship, and the blocks appear to be part of a crackdown on internal dissent in both countries.
Why aren't they blocking telegram too? Is it because they use it a lot and can't block it or because it is compromised, so they have access when needed?
On April 16, 2018, the Russian government began blocking access to Telegram, an instant messaging service. The blocking led to interruptions in the operation of many third-party services, but practically did not affect the availability of Telegram in Russia. It was officially unblocked on June 19, 2020
Some say it was unblocked because they made a deal with Durov. Another opinion is that too many people and services including officials continued to rely on it even during the time it was blocked. Regardless, Telegram did a huge job on circumventing those blocks.
Telegram isn't circumventing shit. You cannot circumvent a coubtry-wide block. If I learned anything from Russia it's that they are very determined when it comes to stuff like that.
I think you are answering your question yourself. There's nothing you cannot fully block, unless it uses vpns/proxies and then you can try and block those too.