For Kerbal, have you tried !ksp@lemmy.world?

Ah, no, I have not! I did try searching “kerbal space program” in the Communities search, but it only came back with a result from a dead instance. Looks like that instance completely lacks any reference to the full name of the game, which is why it didn’t show up. Rather incidentally, that’s why I made a deliberate choice to have the AoM community be !aom but have its display name be “Age of Mythology”. I knew people might search for either and wanted both to work.

Looks like the KSP mod is absent, or I’d suggest they do the same.

Thanks for those other community suggestions. I might take the opportunity of the upcoming expansion (I’m expecting a lunar new year release date, given it’s a Chinese civ) to share in those communities. I’m just very wary of being seen as overly spammy. Most of my promotion thus far has been looking for threads where I can respond by talking about Age of Mythology in the comments and linking it from there.

I don’t know how popular AoM is

Definitely not as popular as those others. That goes back to my original point. There’s a significant network effect in a site as big as Reddit, and it’s hard to blame individuals for not leaving if their smaller, more niche interests are not catered for on the new site yet. Even though, chicken-and-egg style, if they did all move at once to Lemmy, there would instantly be all the space for all the same communities to thrive.