The cutoff for reporting sales is the end of the calendar year, not the tax filing date. On your 2021 tax return you only report sales IN 2021. Any sale after December 31, 2021, goes on your 2022 tax return. It doesn't matter whether the sale is before or after the filing date. Until you actually sell something, you have nothing to report on your tax return.
Using Ethereum, or any cryptocurrency, to buy an NFT or anything else is a sale of the Ethereum that you used. You have to report that sale on your tax return for the year that you used the Ethereum to purchase the NFT.
If you sell an investment at a gain after holding it for more than a year, it is a long-term capital gain, not short term. If you held it for a year or less the gain is short-term. This applies to an NFT or any other investment.
The purchase date of the NFT is the date you bought the NFT, not the date that you purchased the Ethereum that you used to buy the NFT. The Ethereum and the NFT are two separate investments. You can't pretend that they are the same and ignore the exchange of Ethereum for the NFT.
