Hopefully you didn't give up after this.
Just out of curiosity, why not stream to Youtube, Odysee, Twitch, or Dlive? Maybe even Trovo? I've not heard of VIMM.tv so I'll check that one out.

You mentioned Caster.io which I'm also not familiar with, but I'd assume it's sort of like a Restream service?
I don't really live-stream much, but I have a video on my channel about setting up a Linux server as VM(virtual machine) with NGINX and SMTP protocol. It's relatively simple or at least if you're familiar with Linux systems.
But with that VM I am able to stream from OBS to the server running at my home, and it then multi-streams to platforms you enable. In my case I was able to simultaneously stream to Youtube, Twitch, and DLive. You can even have it re-encode for things like Instagram etc.
Just thought I'd mention that.