Average Russian knows more about VPN than most others because of tons of restrictions. And telegram only helps with that by providing workaround and info about proxies.
doesn’t care about who can read and influence their communication
Groups chats are private by default, you have to change that by yourself to make it public. There is no evidence that anyone else would be able to read it whatsoever while it’s private. The only danger comes from actual members who may invite unwanted people or share screenshots of the conversation.
the company behind Telegram has been involved in various sketchy situations
That’s the only thing you have. Any other company that could provide a service with similar features would have to be involved in very similar sketchy situations and there is no way around that. Signal doesn’t care about public communication features which puts it into a whole different weight category. Also signal would hardly care to help Russians restore access if it gets blocked.