The subreddit is r/Moena, I also have a discord https://discord.gg/HC4NkGkU but there is literally no one there.
As for 4d Miner, I actually launched a similar game last year https://medenacci.itch.io/moenablocks. I stopped working on it after he launched because it's basically the exact same game just with a different compass and movement mechanics.
I reached out to Mashpoe on Reddit but he never got back to me. It's a shame because I see him talking about his progress and he's redoing work that I've already done.
At this point I'm considering making Moenablocks open source, I'd need to do some cleanup work before it's ready for that though.