Hey la_cues, glad to see that you're still here. I'm seconding what Myocarditis-man said. Give GNU/Linux a try. It has rough edges, but picking affordable hardware is easier. If you insist on getting a Mac, then take a look at this chart to determine what the latest macOS version is that's still supported. The newer you go, the longer it'll remain supported, but it'll obviously be more expensive. You could buy a somewhat recent model second-hand or maybe refurbished, and you don't have to pick the highest end model. A Mac Mini may be a better choice. I think that suffices for light video editing too, although I'm not sure; you'd have to double-check that. It can definitely handle web apps.

(Of course, a Mac Mini requires a separate screen, but that really isn't so difficult to setup. So long as you don't have to move the setup around a lot, there's no need to insist on getting an iMac.)

I also want to mention the Hackintosh route, but although that's become easier over the years, it may still be more effort than what you're looking for. I get the feeling you just want a good deal and be done with the matter. In that case, I'd evaluate whether or not you care about security. A 2010 iMac supports High Sierra, which is already outdated, but if you apply patches you can install Monterey (macOS 12) on it. Plus I'd look into upgrading the RAM to 8 GB or more.

Maybe consider getting a 2017 iMac. It costs twice as much, but it has 8 GB RAM and supports the latest macOS without any patches and it'll remain supported for a long time to come. This will definitely suffice for your needs.