I've been using linux since way back when one had to be a bit of a geek to install it on some machines (laptops more than desktops since hardware varied more on laptops). As for servers, Windoze and Mac have never made any serioius dent in the *nix dominance. Plus of course MacOS is built on a *nix base (FreeBSD -> Darwin).

A couple points to add:

- Linux is also great because one has multiple window managers (what makes your desktop your desktop) to choose from. Instead of being forced to use whatever annoying paradigm and bloated code the dogmatists at crApple or MicroSlobs shove at you, you can choose from at least a dozen major and many more minor options for your desktop environment. And switch between them easily if you have some reason to.

- Open source software mostly all works better on linux because it's usually developed and tested there first and most. And aside from personal preferences for specific proprietary software (and architectural CAD, alas), pretty much everything one needs is mature, full-featured, and available open source, from office suites to DTP to image creating/editing (raster and/or vector) to audio and video creation and editing, of course browsers and mail clients, development environments, a great pile of quirky and geeky odds and ends, and so on, and on.

Side note - fun to read you were using a T420. That's what I'm using right now. Have been for years, since I upgraded from a T400. Awesome keyboards! The best ever, for frequent and fast typing. I also have an X230 as a more portable/backup machine. I'm thinking of dropping a couple hundred bucks on a used T460 one of these days...nothing wrong with the trusty T420, yet, but all hardware has a finite lifespan so better to upgrade before something dies of age than after...!