This. Or just pay medical expenses out of pocket.

My plan is to keep the minimum required with Optum and transfer the rest to an investment fund with Fidelity, as frequently as possible to avoid incurring costs. My HSA will be fully funded for 2022 by late spring so I'll plan to transfer no later than at that time.

That said, if a bad situation arises, those investments can be liquidated and the funds used for qualifying medical expenses. Of course, the investment funds are not guaranteed in any way, so there is a risk involved, just like with any investment. The philosophy is that if the holder of the HSA keeps the fund active and funded for a long time it will grow and it's a great tax-advantaged way to save money as long as the saver knows the rules and restrictions of an HSA.

The primary reason to look outside Optum is that their investment options appear to have changed for 2022 and they no longer have desirable funds with low fees.