FWIW, you can get purchase[0] up to an additional $5000 a year in paper format if you overpay your Federal income taxes and request the refund be paid as a paper I-bond.
It also seems like you can pay an extra $5K in estimated tax in December, use the refund of it to buy a series I bond and then convert that to an electronic bond.
seems very useful for a $10k investment, if it's going to make a considerable amount for that $10k.
It's breaking even based on the current rate of inflation. It doesn't yield any positive returns.
The $10K limit is for I-bonds. If you want more inflation protection from the treasury, you can buy TIPS up to $5M.