Well idk if this helps you, but Telegram is an arm of Russian tech billionaires, their server is closed source, and true e2e is only enabled for 1-1 secret chats and 1-1 calls. Telegram is therefore basically just an HTTPS-style encryption for almost all its features and kind of questionable affiliation and security
By comparison, Signal is fully open source including the server, and is all e2e, and can be compiled without Google services. But it's also pretty much fully funded by the US govt, so who knows