Telegram's secret chats are e2e encrypted as well. They're not the default option because it's their way of balancing between being a messenger for privacy nuts and a social network with huge channels full of media at the same time.

Comparing the end-to-end chats, I straight up don't trust WhatsApp, it could send my messages straight to Zuck as far as I'm concerned. Given how many reverse engineering projects got closed after a cease and desist letter from them, I suspect a great deal of security by obscurity. While Telegram isn't much better with it's ridiculously convoluted code, it's inviting people to check and they have verifiable builds, that means that they are at least confident in what they are doing.

As for Signal and Matrix, I don't know a single person who uses either, so for me Telegram is the best middle ground for my normie purposes