New RX9 has ARA Spectral Repair connection in Logic

Can/will Cubase create an ARA connection for RX9?

Unfortunately not. At least, RX 9 doesn’t appear as ARA module in Cubase 11. If I understand the information on iZotope’s website correctly, RX’s ARA support is limited to Logic.

But what is the explanation? I thought ARA2 was a common protocol …

Yes, that’s true but technically it’s an extension of the VST, AU and RTAS specifications. I guess, iZotope only provides AU versions of their ARA plugins and no VST ones.