This could be quite hard without JP1.

I found a few bits of info:

In this FAQ from Oppo
[Link: oppodigital.com]
it says:
Q: What is the universal remote control code for the OPPO OPDV971H remote controller?
A: The code is "49B6". If your remote does not allow you to enter letter "B" try "49116" because "B" is "11" in 16-bit.

I doubt there is ANY universal remote in which you can directly use that information. I think the folks at Oppo are seriously confused about how universal remotes work. BUT to an expert, that statement is a strong hint that they use NEC protocol, device number 73 (which would be a big help if you use JP1).

I also found this:
[Link: remotecentral.com]
which gives the Oppo codes as a mxd file for an MX-700. Unfortunately I don't know how to extract Pronto Hex or other formats I might understand from an mxd file. Probably some other expert here does know.

I did look at the raw contents of that file and at least confirmed that it is NEC protocol, device 73.

I looked in Rob's list of OFA setup codes and found only CBL/0248 and SAT/0358 use NEC protocol, device 73. If you had either of those setup codes all the buttons would be wrong, but could be moved around with KeyMoves to make them right. Unfortunately those setup codes are only in European and/or obscure models of OFA remote, not in the models you are considering buying (nor in the RCU810).