My wife and I both bought I Bonds directly. It was not exactly a painful or confusing process at all. Granted, the UI/UX of the US government bonds website was not fantastic, but it was certainly usable.
The UX is awesome and the layout is simple: no popups, interstitials or other BS. Even better, the page load times and responsiveness are significantly better than any other financial website a visit. I can check log in AND check my TreasuryDirect balance in about the same time it takes me to log into my Schwab brokerage account or load a thread on Reddit.
Their FAQs are also written in an easily understandable way, which is good because I Bonds and the other bonds they sell have some complicated nuances. They even update the FAQs regularly so that all their I Bond example calculations use the current semiannual interest rate.
One thing that would be cool about this Yotta offering is if they automate some of the I Bond annoyances (I needed a medallion stamp to open my account although not everyone is that unlucky), give a consolidated view of purchases and holdings across across multiple SSNs and EINs, and centralize that management.
Do you support cleanly setting up POD beneficiaries? Do I need to give you my spouses' SSN for that too? Or do they also need a Yotta account?