Yes indeed I use it, it doesn't refute my statement.

Which ones don't? I used the Android client and telega, both of those do. I believe the iOS one does, too.

The web client doesn't seem to support it, or at least I can't find it -- it's definitely not in the contact/profile screen like in the Android app.

For sure: Linux.

I use telega on Linux, I guess this is the Qt-based desktop client?