There are a few approaches I’ve seen that sort of make NFTs somewhat fungible assets…
You can fractionalize an NFT (like having shares in the NFT and when it sells, proceeds go to the shareholders), you could then trade the shares as ERC20, but not the NFT itself.
You can create a basket of NFTs and fractionalize that, which is similar to the above but is sort of like fund. There are lots of questions about how this is curated and how and when NFTs are liquidated. I wrote a post about how we could adapt a gardens dao for this purpose a while back and still think its a cool idea: Gallery: Gardens + NFTs
You can create semi-fungible tokens, where there are multiple NFT of the same class, which can be transferred in batches, but likely need a specific type of exchange to trade these.
There may be others as well but that’s what I’ve seen so far. Its an interesting area for sure!