It doesn't matter whether NFTs are classified as collectibles......if you hold them for investment purposes rather than for personal use then you can deduct the loss.....as a capital loss unless they were somehow business property.

I indeed hold them for investment purposes so I understand now I am able to deduct a loss. Now what about trading them: I sometimes like to trade one NFT (A) for two others (B and C) because it provides me with options, even when this means at times that B plus C is worth less than A (meaning a loss for me). This happens for example when I sell one expensive NFT for two cheaper ones for easier re-sale in the future. Question: how do I value this trade for tax purposes? Do I for example take the last known sale price of B and C and add those up to determine the sale price of A?

Yes I would think it would be FMV.....market value.....which would be both your sale price for A and basis for B and C.