Hey Team,
Just letting you know when I downloaded the 8.4.0 RC 2 firmware onto my BR1 Pro 5G, the 5g wifi was not working at all. I could not find it on any wireless device, even though all of the AP setting were correct. Moved it back to 8.3, 5Ghz wifi back to normal.
You might get better results by posting this in the main RC2 thread. Nevertheless, I just looked at my BR2 Pro 5G which shares some similarities and I see both 2.4Ghz and 5Ghz for multiple SSIDs. Have you tried applying the firmware a second time (same firmware file, just a second time)?