Schrittmotoren brummen im Stillstand

Yes, I think so too. I had so much trouble and put so many hours into this. I have ordered another PC (I found a recommendation in this forum) and hope I will be able to make everything work with that PC.
Anyway I am so thankful for your help and efford.
I am able to prepare the HALs, INIs and Configs for the new PC and I have learned so much about linux and linuxcnc.

Remind me, what PC was this?

Lenovo ThinkCentre M710q Tiny Mini-PC (überholt) Intel i5-7400T RAM 8GB SSD 240GB

The very small one with power brick?
I have one of those somewhere...

I don't know. It will be here on wednesday. I can post the info I have here:
Intel Core Prozessor i5-7400T 2.40 GHz (bis zu 3.00 GHz in Turbo-Boost / 4 Core 4 Thread)
Integrierte Grafikkarte Intel HD Graphics 630
RAM-Speicher 8 GB DDR4 SO-DIMM 2133 MHz – RAM maximal 32 GB unterstützt.
SSD 240GB SATA 2.5"

Front:
2 x USB 3.1 Gen1
1 x Kopfhörer.
1 x Mikrofon.

Back:
4 x USB 3.1 Gen1
2 x DisplayPort (Video).
1 x RJ-45 LAN Port 10/100/1000 Mbps
1 x Netzteil (externes Netzteil mit 65 W Original/kompatibel).

2 x DDR4 SO-DIMM RAM Steckplatz (variable RAM-Bankanordnung)
1 x SATA III Stecker (1 belegt)

Maße des Computers: 17,9 x 18,3 x 3,5 cm.
Gewicht des Computers: 1,4 kg.

Hey, I want to give you a quick update of my journey.

The Lenovo ThinkCentre arrived and I followed the instrucktions of the sticky posts in the QtPyVCP part of this forum. It worked very well at all for me and so after a short Intermezzo (booting with any other OS than windows is blockt in BIOS by "safety reasons") and turning off all unnecessary BIOS options I got a running ProbeBasic on 6.1.0-7-rt-amd64 #1 SMP PREEMPT_RT Debian 6.1.20-2 (2023-04-08) x86_64 GNU/Linux.
Ping is about 0.470ms
servo jitter up to 135000 if I stress the PC with glxgears and changing the window size very fast.
I isolated core 2 and 3.
So definitely some space for improvment but I had no "hm2/hm2_7i96s.0: Error finishing read!" yet and only one warning that the servo threat is too high (put it to 1000000 now) at the very first start up but never again.
So I decided to play a bit with my newly achived success and set up the stepper parameters, moved a bit by hand, set up the tool leingth measureing routing and finished my tool table. I can tell you, I really needed that, I am feeling a bit exausted about this project.

So right now I try to set up my spindle but I will open up another threat for that.