This is incredibly simple and something we should have done anyways I suppose.
So here’s what you do - take a topic url, delete the postcount, add “/print?page=” followed by the page number you want.
This will give you 1000 pages of the topic ready to be saved as a pdf.
Discourse throws a fit if you do too many at a time, and although I could get around this with private browsing I’m busy with finals, so I’m crowdsourcing.
Do that with a handful of pages, rename the pdf to include the thread title and page number, throw them in a zip folder, and send them to my throwaway spam e-mail.
We’ll start with the cookie thread, but realistically could back up anything in .pdf form. It’s not ideal, but it is what it is.
I’ll make the second post a wiki - if you save something, edit yourself in with the page you’re saving so nobody else wastes time or storage space on it. At the end, I’ll combine the .pdfs and put them on Google Drive or something. Simple, easy, everyone can contribute a bit.
If you really want to go above and beyond, you could always put in the research and legwork over on Meta to try and find a better way to download things than .pdf, although they pretty much all require an admin’s help, so you would likely need some help to actually implement it.
Good luck friendos