You would need a valuation for the painting you disposed of. The fact that you never actually received USD is irrelevant. I had this problem in 2018 - I bough

You would need a valuation for the painting you disposed of. The fact that you never actually received USD is irrelevant. I had this problem in 2018 - I bought BTC in 2017 before the boom, exchanged a bunch for ETH at the peak of 2018, and then rode the ETH all the way back down. I had to pay a bunch of taxes on the BTC gains I “realised” even though I didn’t get any actual cash out. I had to pick a price settle for BTC/USD on the day I bought ETH.