A few months ago we've open sourced Mashroom Server, a platform that allows you to easily build Web-Portals from Microfrontends (either server-side rendered Express.js web-apps or client-side SPAs). React, Vue or Angular apps can be developed completely independent (and without any lock-in) and then later integrated into Portal pages (even via Drag'n'Drop). The platform also comes with security, theming, i18n, storage and communication out of the box.
Version 1.2 has just been released today: https://medium.com/mashroom-server/mashroom-server-1-2-released-f4e5502d855d
Check out the homepage for the current features: https://www.mashroom-server.com/