Mesa Ethernet / QtPlasmaC retrofit experience — lessons from a marginal mini PC

You are welcomed, always.
P.S.
Wait till you figure out what you can do in HAL !
That is the main thing why i liked it so much back then, for me it just clicks "connect this pin to this pin" and it works!

Choosing a computer for LinuxCNC is always a lottery and it is impossible to give any universal advice.
A computer that works great for you may not work for me with my version of Linux, my version of kernel and my version of LinuxCNC...
For example, I use AMD computers (A10 and Ryzen), also with Realtec NIC and MESA. I have read several times on this forum that they do not and will not work with LinuxCNC and especially MESA, but they work flawlessly and I am very happy with them.
Even if you gave a specific computer model, motherboard revision, operating system type, kernel version, LinuxCNC version, it would make some sense, but tomorrow some developer will change something and something may stop working...

I've always had good luck with used PC's for LinuxCNC, mainly because i always use the "Enterprise" versions from Dell, HP, Lenovo, and Fujitsu.
Same with Mesa, i am sure i have Intel and RealTek network cards in use, none had any issues, ever.
Then again, i have several USB to LAN adapters that work fine with Mesa, Laptops and tablets that work fine with Mesa, etc, etc.
I would roughly say i had about 0.5% rate of not working/not usable PC's, and 30% rate of not usable laptops.