philjw49 states that both PCs are now working. KB5013943 was no longer present in the downloadable updates.
I have a brand new XPS 15 9510 and XPS 8950 both were bricked yesterday by the latest MS critical update KB5013943. I have no idea why MS would release such a buggy update. Had to spend 6 hours recovering both machines back to a usable state. I've put future updates on hold for 2 weeks in the hope MS will pull this update and debug it before issuing a new one. Beware download at your peril. Does DELL have any involvement in testing updates to ensure compatibility with their equipment and builds? I thought we were through all this sort of nonsense from MS after the various catastrophes in the past - obviously lessons not learnt yet! 
Lates Windows 11 Update KB5013943 - Critical Issues - Beware!