MAC address not retrieved (after 2 years stop)

Those are fairly dismal ping results, What is the Ethernet hardware?
If Intel, make sure you disable IRQ coalescing (see hm2_eth manual page)

 

I'm really poor in network matter....
Why my results are so dismal?
I red "60000 packets transmitted, 60000 packets received, 0% packet loss" and I was almost happy.....
BTW, the Mesa in wired to the onboard ethernet card, while the router (LAN, WEB) is wired to a PCI board (a commercial, very cheap one, this PC is intended only for CNC machining)
At the moment I don't remember the MB specification, but as soon as I can, I'll check e post it.

Ok, here you find the specs of my system:
MB Asrock Q1900M
Intel celeron J1900 1.99Ghz
RAM 8 Gb

About the onboard LAN section:
- PCIE x1 Gigabit LAN 10/100/1000 Mb/s
- Realtek RTL8111GR
- Supports Wake-On-WAN
- Supports Wake-On-LAN
- Supports Lightning/ESD Protection (ASRock Full Spike Protection)
- Supports LAN Cable Detection
- Supports Energy Efficient Ethernet 802.3az
- Supports PXE

The PCI LAN card:
EP-9602GS
Chip Realtek RTL8111F
10/100/1000Mbps
PCI Express x1
Port RJ45
IEEE 802.3, IEEE 802.3u, IEEE 802.3x, IEEE 802.3ab
Auto MDIX Yes
Full Duplex Support Yes
Jumbo Frame Support 9k max
MTBF 376,212 hours
Supported Protocols CSMA/CD

try sudo apt install r8168-dkms which is the driver for your R8111 (requires non-free)
Follow my YouTube tutorial for PREEMPT_RT tuning for a detailed process to tune your kernel and the steps required to install this and more
www.youtube.com/playlist?list=PLG0NtQtZP...aAlFBsmYP1ay8VNQwsyY

 

Now the linuxcnc error is once again about the mac address (as in my first post)
Then, I tried to install the drivers for the lan card as you suggest, but this is what I get:

and trying to follow your tutorial on youtube, as soon as I try to install grub-customizer (at the very beginning of the tutorial) I get this:

this is a bit tricky because you need non-free in your sources. This is included in our ISO
skip geub-customizer for now