It's been a while since I played with telegram bots, but I remember thinking it is one of the best APIs I've used. So simple to register a bot directly through the chat interface with the not father, and a 5 second job to add message posting to a bash script etc.
I have had so much fun integrating with Telegram from Elixir. There is a lib (not in hex unfortunately) that makes it all quite straightforward.
I even gave a remote talk about it with an interactive demo: https://youtu.be/DFGHaER6_j4?si=sooEsiyVTmfXPqNs
Telegram is a mile simpler to get going with than the others.
I poked around with doing a Slack bot recently and the hoops for an app were many and confusing. Not Google credentials level but more than I cared for.
I've used both Discord's bot API as well, and can say it was way more convoluted to get up and going. Telegram's API was a joy to build in. This was in Node.js.