Asus never disappointed me, I have Linux running on a 16 year old eeePC and on a 1 year old TUF gaming notebook.
Two friends of mine have it running smoothly on ThinkPads.
I would never buy HP again, to run Linux on it. It was and is such an effort to get and keep it running with HP being so restrictive regarding BIOS, drivers, and so on.
My story is quite similiar, though I was working in theoretical ecology. Turned out that I could handle the computers we were working with and their linux distros better than anything else. I went on for another 2.5 years and then quit. I aquired he LPIC-1 and LPIC-2 certificates from the Linux Professional Institute, worked as a pure Linux sysadmin for half a year and am now working as a sysadmin for Windows in Linux in my 5.th year.
Where I live you need at least some kind of certificate (or some on the job experience) and the will and ability to learn. In my experience most companies that are working with Windows will be quite happy to hire someone who doesn't shy away from the terminal and/or cmd.