They have a beautiful native macOS app as well. Also, excellent support for groups, including group URLs you can stick on a github page. Great program all around.
When you say "desktop" version, do you mean the cross-platform one that offers downloads for Win/Mac/nix, or the specifically Mac version that has a whole lot less features (at this point) than the cross-platform version?
Judging from recent updates it's still alive. The version in AppStore might be stale (not sure) but if you install the version from site (https://macos.telegram.org) you'll get frequent update.e
But I must admit that amount of clients is confusing.