Angular 10 upgrades appear to work quickly with little problems..
The Angular support folks read all issues and will respond quickly.
The Long Version
I became highly frustrated with an Angular 8 refactor project recently, I had seen everyone of these errors below. You know it's true because, nobody could just make up these awful messages?
The effort to resolve them was two weeks! Having even tried a migration to 9.lts, it made things worse. I almost made it but the Angular folks kept asking me if I updated to 10.0 because many of these were fixed.
I gave it a shot, and the good news is that the Angular 10 upgrade experience was good. I did see peer dependency issues due to their calling out pre Angular 10 dependencies (was forced to ignore them). Two projects, one a library and the other an enterprise application were done in 2 hours!
The best part was after two weeks I was where I started, refactoring existing code.