But I've had 2 full time jobs, an internship, a dozen freelance gigs, 3 schools, maybe at least 5 interesting side-projects, I can't possibly fit everything on one page
How do you decide what to keep?
If you show too much stuff, or you don't focus their attention on the most important things, you run the risk that they're going to assume you job hop every few months and they're unlikely to want to hire you. But I would expect most reasonable employers to understand the difference between side gigs and interesting projects you've worked on, versus actual jobs.
In my bio for my 30+ year career, I list a bunch of previous employers and companies I've consulted for, and some previous projects I've worked on. It's pretty lengthy. But a bio is not a résumé. You may want to have both, but you need to be careful to separate them by function and focus.
List most recent full time position
List second full time position
List freelance/self-employed as a position, and maybe highlight your best accomplishments doing that, and more broadly the general skills of self-management etc, but I wouldn’t rattle off each position.
List educational achievements like just your degree and major.
And then, in terms of your side projects, maybe just highlight the ones that are most relevant to whatever job you’re applying for?
I tailor my own resume to each job I apply for, which means, sometimes I don’t include all my work experience, or all my educational experience. When I used to list all my qualifications, I often got feedback “you’re too overqualified” - so I stick to what is relevant to the role.
Also, while I understand the point of the one-pager, with the massive number of applications I see, a one-pager that's light on relevant info is going to get passed over in favor of a longer resume that highlights germane skills ans experiences.
Nope, they only show you enough to let you know they have something you want, and they do it within the limits of a regular advertisement.
You need to do that, too. Keep your resume short. It's not a CV or an autobiography. Keep only what you hope will sell you to that particular company, and don't bore them to tears with so much detail they can't get through it.
To answer your question: Perhaps address skills, tool and on the job experience in one section, and a simple chronological list of engagements in another section.