[joncfoo]

Micro-frontends are indeed a solution looking for a problem as others have noted. They remind me of the ball of mud that was Java portlets.

No team(s) wants to maintain a SPA written in multiple frameworks. If you truly must, embed a component written in framework X into a component in framework Y.

The embedding of components is a good way to re-factor your way out of having multiple frameworks and migrating towards a single framework. We've been doing this successfully at work where we're incrementally migrating our AngularJS + React SPA to Vue one component at a time.