Does it need to be on Renshuu? Setting up a room on something like Owlbear Rodeo isn't all that difficult. You just need one person with an account (free). Here's me as two different players. Player on the right doesn't even need an account. (I've never used this thing before XD)
You weren't really playing actual D&D in the previous thread, so I'm not sure if you need a full VTT (Virtual Tabletop) for anything. I guess a thread on the forums will do, but you'd need to be careful with rule 2.
Maybe you can use a combination of both?
PS: Is the problem that some of you guys don't have access to Discord? Or is it more like you want anyone on the forums to be able to freely jump in?