I heard the amish actually use a lot of technology as long as they don't own it, and of course they still interface with the modern world via commerce e.g. the often run saw mills.

So I imagine they would be confronted by an increasingly bizarre world e.g. imagine of everyone had brain interfaces and communicated telepathically, and they would not be able to talk to people anymore.

I imagine there would be less demand for the things they sell.

Also imagine if people became immortal and any disease can be cured - do they take advantage of the advances or not, and does this affect their retention rate?