High speed logic level converter circuit
There are bidirectional level shifters designed for I2C, that have internal speed-up logic to improve the risetime. These can certainly do a couple of MHz no problem.
Maxim appnote: https://www.maximintegrated.com/en/design/technical-documents/app-notes/1/1159.html
There is also the pass-transistor type, but you need to add strong-enough pull-ups to get the risetime when translating up. Translating down is no problem.
Example: https://www.ti.com/product/LSF0204D