Telekom FTTH in single-family houses - network planning?

For WLAN, it is only advisable to stick to one manufacturer and system. I would also at least prepare the basement for an access point. I personally also use Unifi, mainly because these devices support POE. When the LAN cables come out of the ceiling, make sure there is also a socket in the concrete ceiling or a suspended ceiling to accommodate the cable. I am definitely in favor of POE because no power outlet is needed.

I would also lay LAN in the basement rooms. If you ever make a hobby room out of it, you'll be glad to have LAN. For the TV, depending on the number of devices, maybe also consider 2 double sockets.

In any case, make sure that the LAN cables are laid in conduits so they can be replaced. Electricians resist this the most. But nothing is more future-proof than an empty conduit for possibly a new standard.

Possibly also LAN to the intercom or at least an empty conduit to lay the appropriate cable.

I think it's a pity that there isn't a pinned "expert guide" here for builders regarding this question.

Unfortunately, this is because the local homeowners don't like to use these functionalities of their forum software or don't pay attention to such things on their own. That's sometimes really a shame, because some pearls of explanation get lost or are only found by chance through search.