It's always sad to see a long-standing bit of open-source software put itself out to pasture (a euphemism for going way of the dodo, which is a metaphor
note: ClamAV is a separate, distinct project whose development is overseen by the Talos Group, at Cisco Systems and is not affected by this decision
Yes, ClamTk is "just" a GUI for ClamAV. I wish the article would have listed a few active alternatives. For the Rust humans under us, there is curently https://github.com/ivangabriele/clamav-desktop in development, but still misses a few features. Flathub does not have any other GUI than ClamTk currently. My guess is, someone will fork current ClamTk and work on that?
Maybe one that is written in Rust with Iced toolkit? This could play well into System 76's laptops, for people coming from Windows and expecting an Antivirus tool. I mean at least there is a commercial motivation behind it, so it might get written fast (given how fast they develop the COSMIC desktop environment).