Hmm, not my experience at all.  I just logged into Fidelity and was able to purchase FBTC just as easy as anything else.

Maybe you misunderstood my question.  I want to purchase BTC ETF shares equivalent in value to an amount of BTC that I would send them from my private wallet, without selling my private wallet BTC first (thereby creating a taxable event).  I would still be the owner (so no tax event) but the ETF issuer would now be the custodian.