I tried to use tufte-latex for a longer document in 2012, but bailed out and switched to memoir for multiple reasons.
There are quite some recent questions on tufte-latex here. Its GitHub shows the latest change to this package in 2019. (This is not bad as such, there are a lot of old mature packages.) But seeing questions like this raises some eyebrows.
Is tufte-latex still alive? Would you recommend to use it?
Would you recommend to use it for a 100+ pages document? (I definitely would recommend memoir and I would not recommend tufte-latex from 2012 for this sake. But, hey, a lot chould have changed since then.)
I am most interested in not replicating Tufte's style up to the last inch, but in wide margins, margin figures, full-width figures. Footnote / margin-note citations are also nice. I guess, one could fake all of them in koma or memoir, if one would want to.
(In fact, margin-note citations turned to be a mess in my literature review in 2012, so I switched to more conservative memoir, but a lot can be done in writing itself to fix this.)