Speaking of using other programming languages with Gtk, I've seen https://github.com/diamondburned/gtkcord4 (Discord client written in GTK4 and Golang)

A decent native Qt based e-mail client for one. Kontact/kMail is janky and don't get me started on thunderbloat. Evolution is just perfect and GTK3.

Edward Snowden managed to exfiltrate millions of documents because he was in help desk.