Now that you mentioned it, my Hegel H390 is also gone. Not a real problem for me, because besides accepting Airplay streams it’s also Roon Ready which is what I always use… but it’s odd indeed that it has disappeared from my list of zones in Roon.
I’ll try a reboot once the album I’m currently listening to has ended.
Edit: my Chromecast has also disappeared, just like in this post.