To debug my angular front end, I open the dev tools in Chrome and the sources tab and navigate to the ts file by clicking down through all the folders and when I do find the
Angular uses webpack and all type script files are listed under it. To select your target typescript file, Chrome's Developer tool (F12). Go to Source tab an select "webpack://"->"."->"src/app" -> your typescript file ( See the image file).
Then set the debug line marker on ts file and use normal java script keyboard(F8, F10, F11 etc) feature to debug it.