Supabase is an open source Firebase alternative. Start your project with a Postgres database, Authentication, instant APIs, Edge Functions, Realtime subscriptions, and Storage.

Supabase

Has there been any recent discussion on RLS/Auth support for the realtime functionality/endpoint?

I've checked the discussions and issues on the main repo, and the latest updates I can find are from May, that the team were trying to figure out how to make it scale.

We're mulling over the idea of putting a proxy in front to perform filtering and retransmission of messages, but I figured I'd ask if there's been any progress with getting this implemented into the platform

Looking into this too. 👍 
It's a must have feature in my opinion, I will not use Supabase until it is not implemented.
Any news ? 😄 (thanks for asking)