OK, followup on the Xsaitekpanels plugin suggested by @mjrhealth, what an unmitigated disaster...
Turning on the GNS530 works fine until you hit the OK on the "boot-screen", and the screen goes black instead of showing the map. And the autopilot stops working completely. Like, it enables fine, but it doesn't do any vertical or horizontal piloting...
Looks like I might as well sell my panels and yoke as I have pretty much zero use for them in XP11.