Linux

Ooh, I just did this! Mid 2010 white MacBook, Core 2 Duo P8600, 2GB, spinning rust HDD.

*Strongly recommend switching to SSD. I also added an 8GB stick (so 9GB total, hah) but my hunch is that even the SSD alone would have made this machine much more enjoyable.

I ultimately decided on MX Linux, although with systemd as init so that logind could handle lid and power button events. The default power manager (XFCE?) would result in a black screen upon resuming otherwise. MX Linux also worked the best for me in terms of optimizing for battery life.

PeppermintOS was my second place but also had the black-screen on resume.

I also tried various flavors of Mint but felt that Peppermint and MX were ever-so-slightly leaner in terms of features I actually use and battery life.

Avoid Void Linux. On my system the trackpad only worked in one direction.

I was not able to get the nVidia card to work with proprietary drivers. It's so old that it requires legacy drivers (340) and I just ran out of patience. Nouveau or bust.

I am currently using it for casual web browsing and YouTube. It handles YouTube pretty well although I'm still searching for a native frontend that allows me to login to my YouTube account so I get all my subscriptions and stuff.

I recommend Mint as it's overall a fantastic distro. Better than the majority. And it's not just for beginners. It's full blown Linux so it can do anything.

They have an XFCE version so try that too, as well as the MATE version. All 3 desktops are quite light.

I wouldn't recommend Ubuntu and it's flavours simply because they have Snaps so deeply embedded now it will spoil your experience.

MX-Linux is also a great distro and quite light. Antix is even lighter and maintained by the same team as MX.

Opensuse is always a great choice, and their KDE implementation is quite good. So if you want KDE try opensuse Leap. (Don't use tumbleweed on a Mac because the proprietary drivers for Mac tend to break with frequent updates).

I'm running Mint on my 2012 Mini and it works great. Tried a few others but I find Mint the best.

Pretty much anything with XFCE, LXDE/LXQt, Cinnamon, MATE, a window manager like Sway or i3, or probably some others I'm forgetting, will work just fine. GNOME and KDE are the most popular but the slowest, and from what I remember, Deepin, Budgie, and Pantheon are somewhat slow.

I always used Xubuntu or Linux Mint Xfce. Both have access to the Ubuntu package repository and are easy to use and install.

Debian.