Unfortunately some niches don’t fit with other, larger communities. Simracing, for example, makes no sense in gaming communities, but also makes no sense in car communities.
Do you also enjoy other non-sim racing games? You might post about some of those and then if the opportunity rises also bring up the other simracing games you’re into and direct some folks to a simracing community that way.
It’s roundabout, but I think that’s often how one makes paths to more niche subjects.