Well, in this case I'd be fine with client-side Blazor (WASM mode), as there is a mature REST API and it is an internal app where SEO etc is not important. But

Well, in this case I'd be fine with client-side Blazor (WASM mode), as there is a mature REST API and it is an internal app where SEO etc is not important. But yes, routing is one hassle as well as the complexity for developers etc. We had this issue some when we did the api: ie say an issue was reported - developers would first have to figure out "is this a problem in apiv1 or apiv2, or in the way apiv2 proxies to apiv1?" Absolutely needs to be buy in that we're going to commit to finishing the migration in a reasonable time. I still like that we did strangler pattern for the API vs the "rip the bandaid off" pattern, but it does carry some baggage that can be glossed over in some articles about it.