And it doesn't appear you have an associated working group (WG) for your (expired) draft publication, which could help you identify if you are reinventing an existing wheel..
WebSub cannot be used by browsers because browsers cannot receive POST requests. WebSub is for server to server communications.
Mercure is basically WebSub over SSE.
The draft has been discussed several times on the HTTP WG.
https://websub.rocks/
And it doesn't appear you have an associated working group (WG) for your (expired) draft publication, which could help you identify if you are reinventing an existing wheel..