Here's what Grayscale says in their tax document:
"Because the Trust paid out only a de minimis amount of BTC for payment of Trust expenses during the year and made no distributions of sale proceeds to its Shareholders, under Treas. Reg. Sec. 1.671- 5(c)(2)(iv)(B) neither the Trust nor brokers are required to report the gross proceeds of Trust sales to Shareholders on Form 1099B. In lieu of Form 1099B, this information is contained in the attached 2021 Gross Proceeds File together with an example illustrating how a Shareholder should calculate gain or loss."
So, it's de minimis and not required to be reported. Maybe the whole thing can be ignored.
I may just use zero as the assumed basis. That seems the simplest.
