Almost all Hitachi TV's use basically the same IR signals. Those are in almost all OFA remotes as TV/0145. There are a bunch of other setup codes that are slight variations of that one, that are each in a few OFA models.

I expect at least three (probably all four) of the Hitachi codes you said you tried are that basic code set. So we can conclude your Hitachi TV isn't like most.

The only Hitachi TV I found data on that DOESN'T match all the rest is the CT2647. So there is a good chance that your model matches that one.

The CT2647 uses setup code TV/0151

I have no idea whether the URC10820 includes that setup code.

Many OFA models include it, or you could get any JP1 capable OFA plus a JP1 cable and easily add TV/0151 (there is an upgrade file already posted).