Modern Front-End Development for Rails: Can't get TURBO_STREAM format in some cases

This isn’t directly about the book contents so maybe not the right forum…but in some of the code apps (e.g. turbo/06) it sends a TURBO_STREAM request and in others (e.g. turbo/01) it’s always HTML, even from a link inside a turbo_frame.

No doubt it is something in my environment. I’ve gone through diffs painstakingly setting every yarn package version etc. to match the working app where different. But I can’t get a TURBO_STREAM in a new rails project or in some of the sample code apps.

I know there are a million combination of versions of everything so this is an impossible question to answer, but any suggestions?! I’ve tried reinstalling everything a million times. The new version of the book is great, I’d love to put it into use but guess I’ll have to wait a few months and try again.