Depending on where you are I would probably recommend looking at used Thinkpad P1/X1 Extreme. They tend to be within your budget if you're looking at a model fr

Depending on where you are I would probably recommend looking at used Thinkpad P1/X1 Extreme. They tend to be within your budget if you're looking at a model from a year or two ago and they work very well on Ubuntu (Debian as well if you look at grabbing non-free drivers for whatever isn't working) and Ubuntu derivatives. While I know there are a few suggestions for gaming oriented laptops, but I'd suggest you are careful going down that route as some of the cheaper models feel very flimsy and if you end up working on this for longer periods of time, things such as sharp edges, sub-par (rattly) keyboard, bad screen or hell, even weak hinges, can be very frustrating. There is also the issue that Linux support might not be as good. I had an E460 and it worked fine for 6 years (I dropped it a few times and someone spilled coffee on it) but even 4-5-6 years down the line I could find replacement keyboard, replacement battery and even replacement case for it. When I gave it to be used by someone else, I had swapped these parts out, paid probably 60$ for them but I knew that the laptop will keep running fine for a few more years. I don't think I could find replacement case/keyboard for some gaming laptop 6 years down the line...? Or maybe I could and I just haven't had the chance to look. To sum up, get an older Thinkpad or maybe even an older Dell Precision.