Does Matrix encryption scale? Telegram rooms have a huge number of participants. Also last time I looked into this, Matrix encryption was also an opt in.
Many people seem to think that Telegram tries to be a Signal or Matrix replacement. I dont think Telegram tries to be any of that. If anything you can compare it to Discord, except much better.
To enable synched e2e conversations accross many devices you also need to synch private keys, which is a security nightmare.