Linux

AFAIK if you buy any computer from within the last 20 years, there's a good chance you can get a 6.X Kernel running on it. 32-bit support is fading out, though. If you buy a 64-bit computer, you'll be able (with sufficient RAM and hard disk space) to install any modern distro on it.

Linux kernel is really good at backwards compatibility, better than any other OS.

Software can be bad at being backwards compatible with older kernels, but you should be able to run newer ones.

Linux broke compatibility with 386 back in 2012. The kernel maintainers also began considering dropping compatibility with 486 late last year, but as far as I can tell they haven't actually gone through with it yet (apparently it's likely to be coming in 6.2).

So, strictly speaking: yes, almost any computer that was ever capable of running Linux should still be capable of running the newest kernel version, with the sole exception of 386s.

Whether it can actually do anything useful beyond getting to a command prompt on a serial terminal is another issue entirely.

Usually, yes.

A great way to breath new life into old hardware is to install Linux.

So long as the computer supports an instruction set from like the last 30 years you can run the latest kernel.

Here's a 133 Mhz Pentium running Gentoo with a very recent kernel.

I'd probably recommend something like Debian though unless you are really pushing the limits of the hardware.

Make sure that device doesn't require proprietary drivers (commonly WiFi or GPU). If the hardware in question needs those and you need the component to work, I wouldn't take it for free because you'd be stuck with shitty support on an ancient kernel.

Most commonly, thio affects broadcom WiFi and Nvidia GPUs.

They just removed support for pcimcia wifi cards, so don't get a 20+ years old laptop that doesn't have built in wifi.

If the computer is modern enough that you'd consider buying it to use, I can almost guarantee that you'll be fine to run the latest distros. I just threw Arch + KDE on a 14ish year old laptop I found, and it runs so well that I may daily drive it for a while just for the hell of it.

At worst, you may need a lighter-weight desktop environment (DE) than some of the pretty ones you see in screenshots. And those are simple to install and try out.

Nearly all hardware support is kept in the kernel until and unless it bitrots to the point of unusability. I've had no issues with a 5.10-series kernel on my 2008 laptop, and I don't expect any issues when I finally get around to upgrading it to 6.x (well, except the usual tedium of compiling a kernel on a machine that weak).

Oh you again, yes Linux supports every normal hardware, and even a lot of crazy ones like Risc-V

On Android the system is bundled with the firmware as it comes from the same people. And for some reason those people dont like providing updates for sane amounts of time, like... 20 years?

Probably yes. As long as it's 64 bit, it will run without issue, hardware dependant. For 32 bit machines, you have to be more careful. The 32 bit core duo and pentium m CPUs don't support pae.

Edit: First Gen Pentium M don't show pae support as a flag but they do.support it. You have to set forcepae for some distros. I read the page incorrectly. Pentium M laptops that have 5 in their model number, like the 735 are second gen Pentium M

In general you should be fine. Might have some issues if you want 32 bit.

Most likely difficulty is if you get something with "weird" peripherals that has gone from support.

A laptop with touch sensitive buttons that was only made by Dell for one model in 2008 is something where you might have difficulty finding support.

Yes, the linux kernel will work! I'd say it's even more likely that wifi, soundcard, etc. work without any problems than if you'd buy a bleeding edge laptop (although these mostly also just work nowadays). The oldest machine I've got is a laptop from 12 years ago which easily runs modern linux, but even much older machines shouldn't have a problem with that, at least not with the kernel.

I have a Surface Go 1 perfectly running Fedora while running an Ubuntu VM at the same time. The hardware isn’t old, but it ain’t powerful.

I also have a 2012 MacBook Pro running Fedora as a f it was a monster. But the Ram and harddrive have been upgraded.

So I guess it’s perfectly fine.

I have the various latest release of EndeavourOS running on a 2008 iMac and a Dell laptop that I cannot remember the model of that is even older.

How old is "older?"

I run the latest Debian on a 10 year old Macbook Pro. Linux has given this laptop a second life as a lab machine - it's still plenty fast enough and it has a really nice screen (Retina) which Debian gets right out of the box with no tweaking. The only thing I needed to do when installing Debian is manually get the drivers for the WiFi hardware during the install (although Debian has the non-free firmware by default these days, they aren't permitted to distribute all firmware and the WiFi hardware in this machine unfortunately happened to be one of those).

The biggest concern is how much ram and how fast a processor of the older computer. Most modern distros use about a gig of ram on startup and prefer a processor made in the last 20 years. If your computer has 500mb ram and a single core 1ghz pentium its gonna choke trying to run linux mint.

Instead certain Linux distributions are specifically tailored to work on extremely old and underpowered computers such as puppy Linux. These are modern distributions with updated kernels but are extremely minimalist in nature.