I used a 2015 MacBook Pro up until 2021 when I replaced it with its M1 successor, the 2015 MacBook went to a sibling where it's still their main machine. Apparently it works fine, a little slow but perfectly usable for decade old hardware.

I'm in a similar position to you OS-wise, I still use my Mac for things I specifically need macOS for but my main OS is definitively Linux these days. I use Kubuntu at work and CachyOS at home, needing a machine with a decent GPU for some of my projects got me back into PC gaming after a decade or so and gaming on Linux is actually good now which surprised me. People meme about the year of the Linux desktop but modern KDE is legitimately really good and certainly the least annoying UX out of the major desktop OS environments in my opinion.