So I would assume that your 401k has a brokerage account option that allows you to invest in funds that are not offered by the plan its self, correct?  Otherwise I highly doubt that any 401k/403b/457b etc would have any sort of Bitcoin ETF available inside the plan itself. 

I'm curious of the parameters that surround utilizing this brokerage account in connection with your 401k..are you paying a fee for it?