In total, 23 patch cables lead to a patch panel in a small storage room in the basement. There is also a 19" network cabinet where I consolidate the rest of the infrastructure:
[*]24-Port PoE switch (Unifi USW-Pro-24-POE)
[*]A Fritzbox (Wi-Fi disabled)
[*]A NAS
[*]A Doorbird I/O controller
[*](sometimes a Raspi or Jetson Nano) :)
We now have a Unifi Access Point nanoHD on each floor and are very satisfied with it. We no longer need the Fritzbox's Wi-Fi and have disabled it.
For the DECT signal of the phone, the reception from the Fritzbox in the basement (in the server cabinet) is actually sufficient up to the attic. Of course, one could also use a DECT base station in a central location, such as the Gigaset Pro N670 IP DECT for about 100 euros. (Other alternatives would have been to extend the DSL signal via a patch cable and return to the network via a second patch cable; have the electrician install the TAE socket directly on the ground floor; use a DECT repeater; or use a second Fritzbox)