Linux

My usual suggestion: Get a generation-old business or workstation class machine from one of the major manufacturers, as a refurb. Mostly meaning keep an eye on Dell Refurbished or Lenovo Outlet - sometimes you can also get a deal on a refurb via woot - for something that appeals to you. The stock is always changing at those, and there are almost always sales/coupons for around 40% off at the first-party refurb stores, so +/- a week of patience can save you a bunch of money.

Business or workstation class machines (think Dell Latitude or Precision, especially the ones with models that start with a 7, or Thinkpad) are typically mechanically much better built than their consumer counterparts, and usually full of reputable components that are connected in standard ways - low end consumer stuff sometimes has issues where they got weird less-common components or connected things in stupid ways to save a few cents per unit that will cause driver issues.

Waiting a generation gives time for mainline kernel driver support to fully mature to minimize driver problems, and drastically cuts the price.

I've had several machines following that advice, and I think the only driver trouble I've had with them has been with unsupported fingerprint/smartcard readers, which I ...don't care about anyway.

Or, if you want a way cheap beater and don't mind some hackin', grab a used/refurbished AUE Chromebook that is on the Mr. Chromebox Supported List. AUE means they no longer receive ChromeOS updates, so their price craters to like $50, and you can flash a normal UEFI payload and use them as a (feeble, storage starved, low resolution) computer. Not a good main machine, but they make fun beaters for experimenting. There are often batches of them being dumped via woot.

...also, don't buy anything with an Nvidia GPU unless you have a specific compelling reason, it'll be a pain in your ass for the life of the machine.