Ethercat installation from repositories - how to step by step

Try this 6.3 kernel I built  linuxcnc.org/docs/2.9/html/getting-start...lling_a_later_kernel
Also check to see you don't have a Realtek network card as per this chapter in the same document
linuxcnc.org/docs/2.9/html/getting-start...ltek_network_drivers

EDIT:  and also isolcpus=1

Isolation cores is basic thing what have to be done after any kind of work with lcnc .. very important like u said..

I do not find my network hardware in that list... My pc has 

Maybe should be problem with kernel ... Because there is 4.19.0.11 kernel ... I have to add new harddrive to boot on your hybrid.iso which looks very nice ...

But kernel have to be replaced with 6.3 because only 2 cores in hardware... Am I right?

Ok, you have an Intel NIC. That is good!. For ethercat, just use the generic driver.
4.19 is buster and I've never used it. You could adapt the how to and getting linuxcnc doc to Buster by changing a few settings.
Everything I have set up recently has been around Bookworm. A couple of guys I know have got Bookworm working with Mesa devices on 2 core machines with the 6.3 kernel. You probably should add the coalescing settings as shown in man hm2_eth. But ethercat is much more efficient so it performs better than the protocols Mesa use so it might not be necessary.

The other thing you could try is IRQ pinning and pin the NIC interrupt to the one Linuxcnc uses (likely the isolated core) You will hhave to google that but the theory is that if both the servo thread (and perhaps the ethercat master too) and NIC are all  on the same core, it will be more efficient

I think your i5 will be fine. I have a i3 that works pretty welll once optimised even with a crappy Realtek NIC.
 

Just installed this, and it's a step forward from my previous test, but still have an initial startup issue so I'll update my other thread shortly.

One minor thing Rod, Git isn't installed by default in your iso.
Also the realtek drivers aren't that easy to install on the H3. I did try following the Odriod instructions ( odroid-h3:hardware:install_ethernet_driver_on_h3plus [ODROID Wiki]  ), but it came up with an error, so I skipped them for now. The generic driver appears to work fine.

From memory, there is now a R8125-dkms driver in bookworm .
My ethercat machine is on Bullseye and its using the default driver OK as the dkms driver does not exist.
I thought I added git to the install. I'll review that when I next look. I had a regression with some things so maybe that got lost too.
You'll need to edit the /etc/apt/sources.list to add non-free-firmware and non-free to all lines starting with deb to use dkms.

I had followed your previous instructions to add the nonfree stuff, but it didn't seem to make any difference. The installer did ask if I wanted to load the correct driver (rtl_nic/rtl8125b-2.fw )from different media, but a quick google didn't find anything easily available, but from my previous tests, the default bookworm drivers seemed to work ok.