Core 2 Duos are slow, yeah. I’ve got an Asus F8SP-X1 laptop from ~ 2008 with a Core 2 Duo T9500, 4 GB RAM, and a SSD SATA drive in it. It was originally a mid-range Windows Vista system. Over its years I managed to upgrade it as far as it could go. It does run standard Ubuntu and Windows 10 - Certainly not fast but it does run. Performance would lean towards unbearable without the SSD. I suspect Gnome isn’t doing it any favors and switching to a lighter DE or distro would help (or maybe just ditching the DE altogether) but since it’s just a spare laptop it’s no big deal.
One of the takeaways from your experiment is if it the system was already crap at running Windows 10 it’s not necessarily going to fare better with Linux, at least if you’re expecting a nice desktop environment. I don’t know if in 2025 we need to equate the “will this run Linux?” challenge on old Windows XP/7 hardware aside from the geek/techie users that want to do something with that old hardware. Anyone else non-technical stuck with that type of hardware isn’t thinking about Windows 10 being retired.
The vast majority of private trackers do not have a “hard” ratio economy like you describe. Most private trackers are flexible to give users ways to increase their own upload ratio without requiring that ratio to be “paid” by another user doing the downloading. e.g. when torrents are freeleech the users get to download for free but can still upload to improve their own ratio. And when there’s bonus systems in place those bonus points can be used to add to the user’s own uploaded data count. And sometimes private trackers have events where they make the entire tracker, or entire categories of torrents, freeleech so a whole ton of users get to download for free and will still be able to seed those same torrents afterwards.
Sure, that could happen too. Private trackers will always get some users that just aren’t going to cut it and eventually lose access to the tracker. In most cases the tracker will just end up adding new users and maintain the total user count. Each tracker is going to be different in how they approach this… I think over time the user churn doesn’t happen as much, at some point there’s enough users on the tracker that are doing fine with ratio and whatnot while the tracker hits its own maximum user count so actually needing to replace users with new signups becomes less of a priority.