Oof, that sounded much scarier than it turned out - could've been a 30 bucks brick!
It's fine, i've already rebooted the box. I'm not exactly sure about the improvements, though.
My MCX311A-XCAT always had all Fs in the GUIDs - shouldn't those be "Globally Uniquely IDentifying"?
While i'm figuring out how to utilise the #SRIOV capability, it'll be a member of br0.
…it couldn't be a simple "virtual-function-count" in my #Netplan yaml, could it? (anyone?)

