In fact, the oldest NFTs were on the bitcoin blockchain. The origin assets of the digital antiquities market (NFTs)
https://rarepepewallet.com/
Bitcoin (via the Counterparty internet protocol) played a very dominant role in the very earliest of NFTs/tokenised assets. This was then followed by a strong shift of focus and activity to the Ethereum chain. Given this history, I have divided the NFT emergence period into what I’ve described as the ‘golden era of NFTs’ (2014–2016) and the ‘silver era of NFTs’ (2017 onwards).
I just don't understand how they claim that those are NFT based on the bitcoin blockchain. Just check their site https://rarepepes.com/ and you will see that all the NFT are listed in Ethereum means you can buy/sell them in Ethereum and not in bitcoins.
Marketplace (Altcoins) is the best place to list them.