Which router works with Ubiquiti devices?

Is there actually a network diagram / schematic of an ideal network installation for a single-family house here?

With router, switches, access point, firewall, etc.

Magenta works with detours. Not for laymen. A diagram is not necessary. Install everything centrally in a cabinet. Router, switch, and then the end devices at the point of use. How extensive the whole thing is and how it is connected also depends on the local conditions. In a single-family house, usually one switch is enough. If there are several POE devices, take a switch with POE right away. Otherwise, use injectors.

Is there actually a network diagram / schematic of an ideal network installation for a single-family house here?

The ideal network installation exists at best for a very specific use case – that is, for a very specific house with very specific residents and their very specific habits and requirements. For example, I have lived in my house for six years and have "completely" redecorated three times due to different usage/requirements, independent of the normal technical progress. Even if this may sound odd to many and of course advertising suggests otherwise, appropriate expertise is also recommended for a "typical" home network, externally if you do not possess it yourself. This includes the selection of components as well as installation and configuration. One could say it requires an architect and a construction manager – similar to house building – who then do the planning and implementation. Of course, if you only need "some kind of Internet," the required experience is reduced, but at the same time the risk that something won’t work increases, ranging from WLAN coverage to specialties like guest networks, Magenta TV, and so on.

Short version:
At least one double network socket in every room.
For WLAN on each floor, a network socket on the ceiling, e.g. in the hallway.
All cables end in the utility room, where the network provider's connection is located (DSL, fiber optic, cable).
A router is connected there, and the network cables go into the router or a switch, then to the network cables.

This way, the normal user covers the majority of application areas but can integrate further components at any time.

Don't forget ancillary rooms, such as garage, hobby room, ...

If cameras are to be installed somewhere, prepare for that as well. Don't forget the outdoor access point either. At least provide conduits for such things.

It's important to familiarize yourself with the various devices before wiring, regarding position and possibly space requirements. If in doubt, consult someone who knows what they're doing, but please not someone who asks the question themselves in a computer forum.

How did you solve that with IP intercom systems? I normally wouldn’t connect that to my home LAN, so a separate switch or VLAN?