I found out nothing, other than the knowledge that I am likely not buying TT products in the future. I received no responses to queries and no resolutions by spending lots of time googling.
I've fallen back to using separate controllers for the 3 Riing pack and the Floe pack, then using both ASUS Aura and the TT RGB app to control the lighting.
I've already packaged the sync controller back up and returned it. I plan on writing an Amazon review of the experience for both the controller and the motherboard --- both of whom claim support for the other product, which does not appear to be accurate (at least as far as "blanket" support).
Claims of compatible products for RGB config definitely influenced the brands I invested in when building my new setup. Very disappointing.