The Britmodeller forums can be found at "https://www.britmodeller.com/forums/". The posts do tend towards UK subjects but cover other nations and general subjects as well.
Aeroscale is part of the KitMaker network which has forums for armor, aircraft, cars, trains, and other subjects. In the armor forum, US subjects seem the most popular, in Aeroscale it's a mix. There's a link on the Aeroscale main page that will get you to the various forums.