These boards mostly focus on Enterprise gear, while most of what you list is SMB stuff. Obviously, 3Com had Enterprise gear before they dropped out of the market in March 2000, then slowly got back in around 2009. Now they are part of HP.
It would be up to the board moderators to add another brand to the list. Extreme is listed only for Wireless, not wired. Other enterprise networking players not covered are Cabletron/Enterasys, FORE/Marconi, Alcatel/Lucent, and others.
TanKII