Yes, I fully realize a notebook is significantly more expensive and less powerful than a desktop. However, I don't have a fixed work place, therefore it has to be a notebook, which I could take to and from office, home, etc.

What do I need it for?
Office work (e-mail, pdf viewer, \LaTeX, internet, etc; all of which could run from a USB device plugged into a ten year old machine)
Programming (mostly C++)
No, I won't be editing or watching movies, nor will I play any new computer games, therefore I suppose I don't have to worry about a graphics card, do I?

My requirements:
full size Gigabit-Ethernet/LAN port (an internet cable is superior to wireless)
reliable machine
decent keyboard
should be able to work for hours without getting hot or noisy
matte anti-glare, non-touch screen

I don't care how many pixels horizontally the display has; however, I'm used to 1200 pixels vertically and would prefer not to have less; fewer pixels vertically means fewer lines of code displayed
An optical drive would be nice, however, I don't need it very often, therefore an external device could also be a possibility
High battery capacity, thinness, and portability are always nice to have, but unimportant for me, because ‎I simply sit down at a desk whenever I use a computer.

I was advised to look for a machine with Intel Xeon, DDR4 2133 MHz ECC memory, and Thunderbolt 3

The only available options I could find are the Lenovo ThinkPad P50 and P70, priced at c. ~3 000 euros upwards, which I think is ridiculously expensive.

Does any of you have other suggestions or alternatives? Useful advice would certainly be appreciated.