Hey Philip

in my past gig we created an app shell in Vanilla JavaScript.

if you wanna know how we have done, the principal engineer in DAZN created a liveproject on Manning: https://www.manning.com/liveproject/building-micro-frontends-with-a-team-based-vertical-architecture

There you can see how we implemented it and how we fetch HTML as entry point for every micro-frontend so we were able to get server-side markup appended in the application shell without waiting to load the JavaScript code