For one, it's the only major messenger that has an actually lightweight, well-written and full-featured desktop client rather than yet another boxed-up web browser. I might be more enthusiastic about using the alternatives if I could use the Telegram client.
It's very bizarre to see all these comments downplaying this, or implying the lack of E2EE by default somehow makes it less attractive to the average user than something like Signal.
Most people care about usability and interconnectivity first and foremost because the majority of their messaging activities are not so sensitive that they feel the need to sacrifice those things for mandatory E2EE. Call that shortsighted if you like, but it's far more common than this "encryption or bust" mindset around here.
If signal or some messaging platform could find a way to be E2EE capable all the time, with all the same usability and design as telegram, without unnecessary restrictions on users, and without it being a completely walled off garden from which your data can never be self-extracted, it would win this argument.
Same goes for things like Tutanota and a lot of these other data prisons that are cropping up which create privacy through taking away user agency.
Until then users will pick what they want for their own needs. Telegram met those needs for many.
isn't only the client side oss? server side logs/libs is more likely. isn't it amazing 30 guys handle a billion users and who knows what sort of ddos is unleashed against them.
Intriguing (and surprising to me that they offer E2EE at all), but there is seemingly no Linux build. I can't seem to find source code either (Telegram Desktop's is released under the GPL).
They used to have a page wittily named "feature matrix", which made it apparent that only Element was really kept up to date, with other clients missing features ranging from channel search to embedding images. I don't know if this situation has improved and whether the original page still exists somewhere.
Several of them have been reporting improvements over the past couple years in the weekly Matrix development blog, and I know at least one of them has both search and embedded images. You might want to have another look some time.