I've worked with a ton of apps migration frameworks in my career. From GWT, jQuery, Angular 1, and several non-OSS ones. The only successful incremental migrations I've ever seen have been via web components.
I'm working with one now that rather than convert from Angular 1 to Angular 9 in one shot is converting component-by-component to web components and working on features as they go. They'd have to stop features for at least 6 months otherwise.
I'm working with one now that rather than convert from Angular 1 to Angular 9 in one shot is converting component-by-component to web components and working on features as they go. They'd have to stop features for at least 6 months otherwise.