I’m going to switch from Windows 11 to Linux soon but first I wish to backup every every data and config files I can in my current Windows installation, even those that wouldn’t natively work in Linux. I know the \Users folder is important to back up, but I don’t know what other directories I am missing.


Users is enough. You won’t be able to restore anything else on Linux.
I wouldn’t even backup users, just your documents or any folders the user has created.
\Username\Appdata\Roaming includes the Firefox profile and Thunderbird E-Mails, which you can restore on Linux AFAIK.
Not sure if your Steam folder can be copied over, as well.
You can, but you really don’t want to except for troubleshooting purposes.
There’s lots like this you technically can do, but man can it get ugly fast.
Mind I say this as having been an app packager since the 90’s - nobody sees and wrestles with the ugly underbelly of Windows DLL Hell and other weirdness like app packagers.
You can’t pay me to do those kinds of data restores or copying today, except for troubleshooting.