so a full clear of node_modules revealed another error. Thanks for providing the example code, it helped me find the solution for the new error.
I had a instance of the type "DayPilot.Angular.Scheduler" in my angular component. After looking at the example code, I switched to using the DayPilotSchedulerComponent instead.
Now it's up and running, and so far so good.
About the bug in Angular CLI, I did get that error, and my solution was to remove the daypilot-pro-angular package from package.json while I was doing the ng update. After the migration was done, I put it back and did another npm install.
Maybe that's what caused this error, and doing a clean npm install fixed any wierdness. Wouldn't be the first time a partial npm install broke something, unfortunately...
Thanks for the help Dan!