I agree with this take.

Sure you could NOT do HSA and invest in bitcoin with after tax money but cmon.

HSA is triple tax advantaged! And it forces you to set aside money for medical bills so it’s not like u avoid going to the doctors because u don’t want to spend your Bitcoin.

I'm late to the game, but I would say (in my humble opinion, not financial advice) that FBTC makes "sense" if you sit on the pile of cash in your Fidelity HSA that can be used only for medical expenses. Trades are allowed, and gains are not taxed. So, your future medical expenses will not hurt that much (pun intended). :-) I'm just saying.