Must admit I'd not even looked about. I don't know of any off the top of my head but I'd be very curious if anyone else knows of any. It wouldn't surprise me if there's a number of closed-source ones in use at scale - it seems to be well-suited to it, in my opinion.
It seems to be used by many large companies but with less open source projects of size. I would be interested in trying this proxy in the future if you do opensource it. I use coolify myself but I’ve not had trouble with the default traefik proxy so far.