Want to preface this by saying that I am not a bookbinder. I've read about it, I've watched a lot of videos, I sewed a single textblock and never bound it because I realized I needed some sort of board or cardstock for the cover and just never went out and bought any. But this is what I've seen.

Reddit.com/r/bookbinding is pretty good

https://www.youtube.com/c/DASBookbinding is my go-to guy for bookbinding videos. Though I feel like you run the risk of information overload there because he does a lot of stuff, from simple beginner projects to stuff that seems pretty high level.

Specifically regarding loose-leaf pages that aren't able to really be sewn into a textblock I've heard of something called the double-fan method for perfect binding (which is how they make paperback books. Basically you slather glue on one edge and wrap a cover around it). Check out this video https://www.youtube.com/watch?v=RO6NGw8oNCQ

One thing that I kinda resent about bookbinding as an interest of mine and something that's stopped me from pursuing it further is that I've always been interested in making big, textbook size books, where each page is a4 size. The problem is that if you want to do this in the traditional manner you need to be able to print on at least A2 size paper, so that you've got four A4 sized pages that you fold around so you can flip through them. And being able to print on A1 size paper would be even better. This is, of course, completely unfeasible for the home binder. A wide-format printer that can handle large paper starts at $600. Some of them go for several thousand. These are printers meant for professional print shops, not home hobbyists. Using A4 sized paper you can bind something that's roughly 6x9, which is cool, but it also feels limiting. I've considered contacting local print shops to see if they could print something bigger, but I never have since I've never been ready to pull the trigger on actually committing to a project.

Anyway, what I've done, though it's a little janky, and might not work for a full 400 page book, is take a few binder clips and clips them along the edge where a spine would be in a book. Works okay but I've never tried it with more than 50 pages.

A lever arch is probably the most sensible option, but then you've got to perforate all your pages with holes. Doing that for long projects, keeping them somewhat neat while you do it, is a pain in the ass in my experience. Unless the university printers can do that for you, then it's a no-brainer.

Edit: random, but I just remember one of my favorite youtube videos. It's "Men in Sheds" - The Bookbinder. It's not a tutorial, it's just a committed craftsman doing his craft, and I love it.