Building without antenna and SAT-CAT cable without conduit?

That’s why we basically want to buy and connect our own hardware (e.g. switch). 8 ports might not be enough for us. We have planned LAN in every room, but only one socket. We actually plan to solve that individually (where we need it) with an access point. Only in the office do we have a double LAN port. In most rooms, if one is installed at all, it will probably just be one access point connected to the LAN socket, which can then redistribute. Everything else is simply too expensive for us. We pay €90 for a LAN socket, a duplex costs €145, each net.

I would add a double socket for the TV in the living room. From my point of view, you should plan a WLAN access point on every floor from the beginning and install a dedicated socket for it. Preferably, the access points should be centrally located and mounted on the ceiling or high on the wall.

APs not centrally but where the most speed is needed (living room, office...).
Preferably on the ceiling.

I would also put a double socket by the TV in the living room. From my point of view, you should plan a WLAN access point on every floor from the very beginning and set a dedicated socket for it. Preferably place the access points centrally and either on the ceiling or high up on the wall.

Ah, forgot, a duplex socket is also planned at the TV, right.
Maybe we could remove a LAN socket from the master bedroom on the upper floor and instead place it somewhere up on the wall in the hallway for a central access point. For one more extra LAN socket, I'm almost too stingy, each costs a hundred bucks... :/

APs not centrally but where the most speed is needed (living room, office...).
Best on the ceiling.

The office will get a duplex LAN socket, our computers don’t connect to the network via WLAN, we play too many first-person shooters for that.
If necessary, we’ll put another access point in the ground floor living/dining area if reception from the utility room isn’t sufficient. But it should be, we currently have a Fritzbox in just one room in the house and it provides WLAN for the whole house, including the upper floor. Sometimes a bit weak in spots, but nothing dramatic. I think a dedicated access point on the upper floor will do the trick for us.

So what I have learned here from, for example, experts : Take a look at the products from Unifi. I myself, as a "beginner" in this regard, am enthusiastic.

Reception has nothing to do with speed. If you are too far away or there are walls in between, you fall back to the slow 2.4GHz network. Therefore, plan enough landos or APs. Repeaters have no place in a new building.

You don't need a socket for the access point! They should just let a CAT hang down from the ceiling! In every room, preferably (min) two separate sockets, partly for rearranging, and also because you already need one for the TV and one for the PC.