Technically you could take any smart contract on Ethereum and Fork it on Bitcoin Sidechain RSK which is a Bitcoin EVM compatible sidechain with 60% mergemined hash power of Bitcoin. The monetary asset for gas on RSK is Bitcoin technically RBTC. IOVlabs has their own RNS infrustructure .RSK that uses their own RIF token and RBTC. https://developers.rsk.co/rif/rns/operations/register/

Not the biggest fan of this approach for many reasons but the option is always there. If you are techy you could also create your own RNS protocol on top of RSK and demand the use of only RBTC for creation of domain names as it is all opensource software.