There used to be. (And there are probably existing alternatives to the one I mention below... )
DelegateCall, which was run by Loom Network (of CryptoZombies fame). It was based on its own DPOS chain, bridged to Ethereum via a relay.
"DelegateCall is a Q&A site for Blockchain and Ethereum-related questions that runs fully on a Loom DAppChain."
It was around for a couple of years I believe. The issues in the early days were lack of moderation, and therefore very low quality posts, to the point where you'd have to dig around to find something useful. (In my opinion... )
It now seems to have silently disappeared...