Telegram has 1 billion users worldwide. Telegram allows to share files up to 3GB, which is huge for game development teams, to share assets, even betas. Telegram allows you to create private servers with chatrooms, categorize rooms, and within the same server files automatically categorize in sub-categories like: images/links/videos, so is another great plus for people sharing work, or communities relying on active feedback loop.
I've been using Telegram since 2021, there's nothing like it. You can try Stoat as it is almost a Discord clone, but has some problems, lacks some discord features, and now due the sudden massive influx of new users leaving discord trying to join all at once. Second you can try Matrix.
But personally I can only recommend what I know first hand, Telegram is robust and a very useful tool, allows full control and respects your privacy.