Ethercat installation from repositories - how to step by step

I try to install ethercat on Rpi with Debian 10. Up to installing headers all went OK, but:
pi@linuxcnc:~ $ sudo apt install -y linux-headers-$(uname -r)
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package linux-headers-5.10.74-rt54-v8
E: Couldn't find any package by glob 'linux-headers-5.10.74-rt54-v8'
E: Couldn't find any package by regex 'linux-headers-5.10.74-rt54-v8'

Please help.

How did you install Debian? From here?  raspi.debian.net/tested-images/   or from an image on the forum? OR just the Raspberian image?
Is it a Pi4?
The Pi is  different. You could try just  sudo apt install -y linux-headers
Expect to get more errors... you are probably on your own but it can be done.

 

OK, I see.

I installed on Rpi4 image from the forum.
But I will probably forget about Pi and install on some other machine.

Thanks

Could somebody clarify something for a relative noob, are these instructions starting from a clean install using the Debian 10 Buster preempt-rt ISO?

I'm just wanting to check, as my new test computer should be here in the next couple of days, so just want to ensure I download the correct starting point.

Yes this works for Debian 10 out of the box but we also show you how to change the keyring statement to install on Debian 11 (bookworm) and Debian 12 (testing)

Hello folks,

can anybody make me clear what means this distributed clock row in .xml config file means please? for example ... 
I am searching more information because I want to tune up DC config by picture in the attachments. All that I know that DC should be placed before any first slave which has DC option in the .xml file.

Which value should be in assignActivate = ??? please?

Thanks foxington