Yeah, "best practice" usually is used to indicate some sort of industry consensus on how best to do something. For concepts that are new, it may take some time for a consensus to emerge. In this case, people may have their own ideas about what will eventually considered a best practice, but it isn't really a best practice, in my opinion, until there's general consensus.
I agree that micro frontends are still in a pretty early phase and many developers are just starting to discover this topic.
That said, many companies have shared their experience with this approach over the last one or two years  and you can common patterns and best practices emerge.
Florian Rappl has conducted as survey with 300 people lately and published the result in an interesting blog post .