Well, there were only 33 signal results found by TVHeadend which turned to IDLE and FAIL after a little while.
I did some research and it seems to be a problem some other DVB-C users are fighting with as well.
My initial situation is:
Software wich is running
- Raspberry Pi OS Lite (Kernel version: 5.4)
- TVHeadend 4.0
Hardware recognized by TVH
- August DVB-T230
What I now ask for is a bit help to get "w_scan -f c -x" running on my system, as this seems to be the solution.