For some of them I'm happy of the investments while for others I'd prefer to liquidate my equities (even at slight loss) because I'm no longer interested in the project or believing in it.
Are there any (low or no fees) ways to find a buyer and sell my equities?
"I am long equity exposure in some startups. I would like to reduce my exposure. Is there an effective way to hedge my downside risk?"
If the basket of startups is somewhat diverse, then the first question is whether you can find exchange-listed companies or ETFs that operate in, or generate revenue from, the same sector. The diversification will reduce your single-factor exposure, and put options on that exchange-listed instrument will give you some insurance in the case of a correlated crash.