Had the same problem with my company's M1 Macbook Pro. All of the sudden, after upgrading to Monterey 12.3 my external displays (Samsung M7 at home and double Dell monitors hooked to a Kensington dock at work) sopped working. Tried all the tricks suggested (rebooting, resolution, etc) with no luck. Then I read on the Kensignton support website about updated DisplayLink from Synaptics (for some reason the apple forum doesn't allow links to the Synaptics domain, but a simple Google search will get you there) for macOS: I installed them and automagically it all started to work again... Hope this helps others!