Gregory's ServerTelegram may be more popular but it lags Signal in terms of privacy.
"Telegram’s messages are only encrypted between you and the server and the server and recipient. It means your message is stored unencrypted on Telegram’s servers and can be read by the company. You can opt to create a ‘secret chat’ in Telegram which provides full end-to-end encryption, but by default, your messages don’t have this level of protection."
https://www.groovypost.com/reviews/signal-vs-telegram-which-should-you-choose/