Linux

Linux mint is a really easy and simple starting point. Fedora and openSUSE tumbleweed are a tad more advanced but allow more selection on your desktop environment (mint uses cinnamon, while Fedora and SUSE have both KDE and Gnome options) and thus can potentially support things like variable refresh rate and, when it gets support from KDE later this year, HDR.

For peripherals, if it's razor or Logitech, it'll just work and have community apps made to configure them. I personally like Keychron's stuff so that's what I use and that's fully Linux compatible, it does require some setup to work though. HDR is unsupported for the time being, but variable refresh (gsync/freesync) is in the KDE Plasma desktop environment under Wayland. On the topic of Wayland, if you want to make use of this new display protocol you'll need an AMD graphics card, as NVIDIA has been slacking with their Linux drivers. NVIDIA is getting better but it's not stable enough on Wayland for the laymen. In the case of only having an NVIDIA, X11 works fine, but it's just missing some features.

Also you won't need JavaScript, 90% of what you do will be through the GUI (depending on the distro), especially once you're set up. I know Fedora needs to enable rpmFusion, NVIDIA repos if on NVIDIA, and install codecs for hardware accelerated playback. Mint doesn't have these issues for the most part, though you'll want to enable flatpak's and consider disabling snaps. Mint already includes a graphical installer for NVIDIA and includes the codecs needed for hardware accelerated playback

Thinkpad T480 is the last of the good Thinkpads and should be more than your Budget

Edit. Corrected typo.

Debian! As far as hardware you'd probably have an easier time with an AMD GPU but otherwise most everything works. Get intel wifi if you can/want wifi.

bunches of refurbished t-series thinkpads out there - t480, t430, etc. apparently the 490 is one to avoid. I got a t470 some months back for $150 - put mint on it and have been very happy with the performance.

I'm adding to the pile of Linux Mint recommendations, though I recommend the XFCE version, as it's lightweight. For hardware, if you want a laptop, definitely go with a refurbished ThinkPad. If you're wanting a desktop, look for something cheap and used. If you aren't gaming, the specs aren't super important

Hey for me it was the same. For Hardware you can use anything. The optimal is a full AMD build Or Intel AMD build but Nvidia could give you a headdic. For distros I recommend something Arch based like Manjaro or EndeavourOS. As DE I recommend Kde Plasma because out of the box it looks pretty much like Windows but is highly customizable.

I think I need to narrow some things down;

My current Windows PC isn’t what I’m looking for; it’s a big and powerful gaming laptop from a few years back. I’m looking for something light and portable, but with a full keyboard for coding.

Pricewise I’m looking for something around $350; if this is unreasonable let me know.

As I understand it, Steam Deck uses KDE, so I’d like to stick with that for now.

Start anywhere, being interested in it is all you need (and a decent search engine, and learning how to describe the problems you have to the search engine). Whatever you do, I think it's a good idea to pick something that will be your project on Linux so that you have a concrete goal that makes Linux useful.

For hardware I'm a cheapskate so I recommend using whatever you already have, but I'm sure others here will point you in the right direction 😹

I recommend dual booting at first with grub, so it's more of a departure from windows. Using a VM like Virtualbox or Hyper-V is a bit safer and easier, but you're probably not interested in Linux for safety or ease of use.

We're lucky to live in a time where if all you have is a Linux tty (no gui, just a text mode shell) you still usually have a phone with Internet to look for help. It's a good exercise when you have the time to try and get the system back up in those situations without external help for at least a few minutes. Most distros still install manpages just for times like these (man and info commands view them)

Thank you.

But literally any PC that’s within your budget. OK maybe that’s not true, there might still be some crap WiFi cards out there with weird firmware that don’t support Linux very well. Find an older name-brand PC within your budget. Before buying it Google “[make and model] Linux WiFi” and see whether there’s tons of complaints about the WiFi. If not, go ahead and get it, put Ubuntu or Linux Mint on there, start banging out JavaScript projects, profit.

Even a smol potato like the Orange pi zero 3 (which -still- has zero linux support) can run Linux, so don't worry about it.