First of all, we need to know that Crypto is just another form of currency, that's why we say cryptocurrecny. It is not gold, not a precious metal, not livestock etc, it is only new form of money.
Now first take the example of fiat money. You have Rs and Dollars. Now its up to you that you convert rs into dollars and pay zakat in dollars or convert dollars into rs and pay zakat in rs. OR you can calculate dollars holdings and pay zakat in dollar separately, while calculate rs holdings and pay zakat in rs separately.
Now, if you do not want to convert bitcoin into dollars, because 1 btc is 1 btc then if you have 1 btc, you can detect 0.25% of the amount from your btc and crypto holding and pay that amount as a zakat. So now we don't need to convert. Also, same should be done with USDT and other coins also.
Finally, isn't it strange that when you need to send money to someone in crypto or buy anything online in crypto, you calculate it in dollars and then send the particular amount in bitcoins. but when it comes to calculation for zakat we make excuses of 1 btc = 1 btc .
agree my dear it's not an excuses, didn't I repeat it's up to you.
What scenario you have given it's your point of view isn't it? Or are you giving fatwa? or are you quoting any Islamic scholar?
again yes you will calculate zakat on your "crypto assets" since those are your investments and you have plans to sale it but how you will calculate its up to you.
Now If I ask let suppose I own an NFT a tweet from jack, I own it no plan to sale it, is zakat due on this? and how much?
Remember
If you hold an asset that is non-sharia-compliant – then zakat would not be due on that in any case as it would be deemed a haram asset.