It’s a bit confusing, because the term “Lean Startup” has become so widely used by so many people that it has become more of a buzzword than anything else.
What I’m referring to when I say “Lean Startup” is Steve Blank’s “Lean Launchpad,” which is most certainly a methodology and its taught widely at many universities and other programs.
Also, while I agree that an “MVP” doesn’t readily apply to many hardware technologies (at least in the same way it applies to software), the Lean Startup method certainly does, even when the technology in question is true “hard tech.” I covered this topic in two articles in HBR:
This article is about the I-Corps program where the Lean Startup has been tremendously successful: https://hbr.org/2017/03/this-program-uses-lean-startup-techniques-to-turn-scientists-into-entrepreneurs
This article shows why the “Silicon Valley” method doesn’t really fit with many technologies: https://hbr.org/2018/04/why-some-of-the-most-groundbreaking-technologies-are-a-bad-fit-for-the-silicon-valley-funding-model
I hope that’s helpful.