Yes, the repository has been archived. https://github.com/hexchat/hexchat

If Hexchat is in Trixie repository (which seem to be the case) it will be maintained across its lifecycle which will be a couple of years. If you’re fine with receiving security patches only, then there is no need to swap the client. As for myself I’ll stick to Hexchat as well for the time being since it just works.