The Uncharted Worlds SubReddit might be a good place to post future design stuff.
What I’ve always really enjoyed about UW is its character creation. You can come to the game with a unique character concept, and every option you choose to build that character will feel really impactful.
I’m not quite sure about Reddit. That kind of posting doesn’t really encourage responses or discussion in a way that I can easily parse. I much prefer this forum-ish format here.
I’ve been checking out The Cauldron, which has a very similar format to this place. It seems pretty active and I’m getting a good vibe so far.
[Edit] Does anyone follow ttrpg designers on Mastodon? How does that work out? Is it mostly announcements “I’ll be at x convention” or “I’m running a kickstarter” or something like that?