I got electron installed again with specifying a version (sudo npm install electron@6.1.12). No idea, why electron disappeared in the first place.
The MMM-MyCalender has indeed an issue with 2.16. causing a black screen. And MMM-Fuel is saying “undefined” for an unknown reason. Both modules are disabled for now.
My MM boots and shows the all other modules again.
With each MM update something crashes, mostly one of the 3rd party modules because one or more dependencies are lost/changed or deleted.
Thanks for your help. Great community!