I recommend one of two Linux distributions, either Debian or Fedora. Both are well established, extensively documented and default to rather libre software friendly . Fedora does include non-free firmware on the install disc so it's a little easier to get going with on some hardware. Debian doesn't supply non-free firmwares on the default installer but you can download and alternate non-official ISO with the firmwares for WiFi, graphics and network cards that need them on it. Please note that not all WiFi or network cards need a non-free firmware so give the regular Debian installer a test first. In my personal life I try to use as little proprietary software, firmware and drivers as possible. I use both distributions on a daily basis and find both to be suitable for almost any task, although I have my preferences depending on what I'm doing. Debian is probably the most universal of the two and I run it on everything from single board computers, large multi node clusters, desktops and laptops. Although these days I've been preferring Fedora on my laptop machines for its more battery friendly out-of-the-box settings.
Why not Ubuntu? Besides making several questionable choices over the years regarding their user experience, data gathering and community fragmentation. Plus, I'm flat out just not a fan of derivative distributions. Debian isn't hard to install, tends to be more stable, isn't run by a company trying to mine data and make a buck, and it uses far fewer resources. Linux Mint or Linux Mint Debian Edition are both recommended over Ubuntu.
Obviously if you want to work in a big corporate environment check out RHEL or CentOS. Fedora is the basis of both of these distributions and tends to have far more up-to-date packages. I only use RHEL when it's specifically required for a project or a piece of software and prefer Debian for my own servers and infrastructure pieces.
I have a few old favorites I enjoy as well but aren't as beginner friendly nor as easy to manage in large production environments. Slackware is worth looking into for more advanced or more curious users. I ran it for years, even on servers. My time is rather limited these days and I don't have as much to devote to fiddling with things as I like so Slackware tends to live on one-off old test hardware. Alpine is another distribution I have been experimenting with lately too, but TBH I can't think of a reason to use it over a barebones Debian install.
Basically anything IBM buckling spring. Model F or Model M. If you don't fancy a vintage keyboard or want a more modern 104-key layout the Unicomp Ultra Classic is my goto. These are not Model M "clones" as rumors claim. They are made with the same tooling in Lexington, KY that the old Model Ms were by many of the same people. They are Model Ms.
Build quality isn't quite the same as the older boards but it will still far outlast anything else made today.
Second place goes to the Alps based Apple Extended Keyboard I or II if you have to use a Mac for work or something. Unfortunately there is no modern version of either of those but both were fairly common and can be found rather cheaply in used shops or recycling centers. Unicomp makes a Model M with a Mac layout too.
I used to use whatever Logitech G518/G400 equivalent was floating around cheaply. They are wired, can switch DPI in hardware, are long lasting and comfortable for right handed users. For an ambidextrous mouse I like the very old school Micosoft Optical Mouse D66. No DPI switching on that model but they can still be found new old stock for under $10. Either is fine, I just like the feel of the Logitech for longer periods and the DPI swapping is nice but I'm not left handed. I've used the D66 for years too.
Now I've become more fond of trackballs. Unfortunately they are less popular so options are more limited and the best stuff is probably only available used. The Microsoft Optical Trackball is the best and most easily found wired thumb ball these days. You will want to replace the likely worn out steel bearings with ceramic ones so factor that into your cost. It's not hard to do if you're competent with a screw driver and a small manual jewelers mini drill. Sadly all of your new options are battery powered wireless models. The Logitech M570 is a good value and uses a bog standard AA battery. The MX Ergo is not worth the price difference IMO mainly due to the non replaceable battery and the rubber coating. That coating feels nice but it'll turn to goo in a few years and get all sorts of dirt stuck to it in the mean time. I would only recommend it if you can find it refurbished or used at a significant discount, which is how I wound up with one.
If you don't have one don't get one. If you do have one get rid of it.