Last time I tried it, I installed Ubuntu 18.04LTS, updated, installed the recommended graphics driver, and then the machine would not boot after that.
I recently tried 20.04LTS on a laptop, with an external GPU over tb3 - it works! However, I really struggled to rectify the display density of my external 4k with the laptop's built in 1080p. I had other show stopper bugs, besides bad scaling, however. :(
What you're missing is the ability to open a game for a quick session while keeping your work open in the background.
What you're missing is that desktop linux is famously unpolished, and worse, brittle. There's a list of known(!) issues with desktop linux that some guy updates - currently it has over 100 entries.
What you're missing is your system continuing to work after major updates (Windows 10's relatively recent and rare "big oops" bugs aside lol). Personally, I use w10 pro with deferred feature updates to mitigate this, which is kinda messed up but there you go. I simply can't afford an update to knock my desktop out, which has happened to me a few times with desktop linux.
What you're missing is that "works for me" works for you, but not for me.
In case you're wondering why I keep trying desktop linux, it's because what I'm missing is an open, free, libre, privacy-respecting desktop. These are values I take seriously enough that I pay yearly estimated license fees to the open source components I use in the form of donations.