https://theins.ru/en/news/273751
Proxy Please: Help People Connect to Signal
Several countries have recently blocked Signal, leaving their residents without a trusted and safe place to communicate.
To help in this situation, Signal provides a built-in censorship circumvention feature and also includes support for a simple TLS proxy that can bypass these blocks in many circumstances and let people communicate privately.
read here https://signal.org/blog/proxy-please/
and here https://support.signal.org/hc/en-us/articles/360056052052-Proxy-Support