use0 alias is used by the 5ghzCode:ifconfig br0:trans 192.168.1.10 up
I think br0:0 vs br0:trans might be a router-specific requirement?
I've used br0:0 for maybe 4 years now on my AC-86U and it has works flawlessly and as intended (both my 2.4 and 5 Ghz radios are disabled FYI).
It appears br0:trans might be needed for newer models.
Just FYI in case others find this useful.