Tender offers.

https://www.investor.gov/introduction-investing/investing-ba...

https://www.law.cornell.edu/wex/tender_offer

https://carta.com/learn/equity/liquidity-events/tender-offer...

https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...

(secondary markets are sometimes an option, depending on stock transfer restrictions)