Good tip. Will check out sx.bet though from first glance it does look light on liquidity.
I'm not 100% on the business model for polymarket. They use UMA so in some ways you might consider UMA to be a governance token of some kind when it comes to resolving events.
From what I understand, sx themselves is acting as a market maker to bring some initial liquidity but still with odds that have quite some juice on them. With feels turned off right now, sx is pretty much betfair with no commission but at the same time with a limited number of users. It's the classic catch22 for everything that tries to be a betting exchange. liquidity is needed to bring users but users are needed to bring liquidity.
I never even heard of UMA, good info to know they are using that.