Why do you feel there needs to be a blockchain involved?  Blockchains are not censorship resistant by default, who will be securing it, whats their economic incentive to secure the chain, who is going to deploy resources to validate the chain? 

Blockchains are awful data management tools 

 I’m no expert, so whatever is going to make it impossible to censor.  

 It's a hard problem to solve, nostr solves it by redundancy, if one relay censors you, your content can exist and be pulled from another, if all public relays censor you, you can run your own relay and no one can take down that instance of your content