I agree that learning to work through boredom is an important skill. But I also think the internet has made it substantially less important because so much more knowledge has been made available in non-boring ways.

I work through boredom not because I like boredom and not because it's "foundational" to somebody else, but because that's the only way for me to accomplish a goal. So to the extent that somebody's particular work still requires it, I think we're going to have to find new ways to structure things to bring that experience forward in time for them.

I think the other option is to restructure things so that being bored is even less necessary. For example, the common way to think about "foundational" concepts is to structure education with a lot of boring and apparently pointless stuff up front, the promise being that it will pay off later. To me that looks like privileging the convenience and perspective of the instructor over that of the student. Can we instead swap it around so that "fundamentals" are taught in slices in close relation to purposeful activity?

As to the Montessori question, I think it depends on your understanding of boredom. My understanding is that as the student gets older, they take on larger and larger projects, so they learn how to deal with the sort of boring that comes from purposeful hard work, but not the sort of boredom that comes with blindly following authority. To me those feel pretty different, and I might more accurately call the first "tedious" rather than boring.