If you're using two different domains for two different websites why not just direct them to two different static pages on one or two of those free hosting sites and then just link to your server using the IP address and then
ip.address/runbasic/seaside/go/ProgramName (or however that goes).
I've had static websites running at
byet.host/free-hosting for years. If there's ever been any downtime I've never noticed it. Just make some static html pages (maybe an "About" page etc.) and whatnot on their free servers, just so you have some content there and it doesn't look like all you're doing is using their service as a link farm. And then just put your links to whatever RB programs you want that particular domain to point to on there (using your IP address) just like you would any web page. They don't force ads on my websites, but I put a link to them at the bottom of my pages as a way to show my appreciation for the use of their servers. I actually have a ton of pages on there that have been host there free for years. Almost all of them have a link to their free services at the bottom of the page. I'm not sure if that's why I've been able to use their service hassle free for years or not. But I'm sure it doesn't hurt.
The only downside is that their servers seem to have slowed down to where rendering graphics can be pretty slow. It wasn't like that at first, but the workaround is easy. If you need graphics, use one of the free picture hosting sites and they'll load fast. I just don't use pictures there. Everything I have on there is informational and I don't feel those pages need pictures. In your case you're only using it as a landing page to link to your server.
If I remember correctly I used to use Flikr's image hosting service and didn't even need an account. I just had to remember to get the image address because without an account I didn't have a way to access the web addresses again. I just saved the addresses and then I could post them into my pages "<img src=" + image address etc. I'm not sure if it was Flikr or another similar service, but there are a few services that allow free picture hosting, usually with a drive space limit. But the one I was using (Flikr I think) anyone could use for free any time, unlimited without even signing up. The only rule was I think you can't have a site where every picture is hosted with them. No problem! use two different free hosting services, or if you already have some kind of cloud hosting like that, just use that.