Basics of wireless smart home solutions

This is roughly my approach and why I tend to favor radio, fully aware that a BUS system is better.

More important than "systems" and "protocols" to me seems to be designing system-neutrally on the level of "network topology." I consider "radio" in the sense of "consistently radically wireless" to be neither feasible nor desirable; therefore, in my opinion, one must always consider where and how to combine the radio and cable components. And even though not everything that is bus-based is bad: I generally find a star topology decidedly more appealing. At the latest when it comes to imagining radio in any topology at all, most neurotypical people become completely philosophically overwhelmed. When it then comes to the number and cross-sections of Siemens aerial hooks for the radio empty conduits, even I like to use a scrap piece of paper ;-)
But mind you: I recommend the OP to remain focused for quite a while on the scale of basics and essentials before attempting any dancing on the fifth decimal place.

More important than "systems" and "protocols" seems to me to design system-neutrally on the level of "network topology".

Which system or protocol change does not also force a break/node in the topology? In this respect, there are hardly any topologies left that could be designed system-neutrally.

I consider "radio" in the sense of "consistently radically wireless" to be neither feasible nor desirable, so in my opinion one always has to consider where and how to bring together the radio and cable components. And even if not everything that is bus is bad: a star topology is generally decidedly more sympathetic to me.

Would you like to give a reason for that?

Which system or protocol change does not also force a break/node in the topology? In this respect, there are hardly any topologies left that could be designed to be system-neutral.

Therefore, I also like to advise against deducing from a current decision for a bus-based system not to keep cables for a later system change.

Would you like to give a reason for this?

Radio links – I also like to call them "wireless cables" – are more expensive and more susceptible than "wires". They have their justified uses but are often simply used out of cabling laziness even where they are unnecessary if they connect components that are non-nomadic at both ends. In practice, signals rarely travel the entire way through the house purely by radio but switch between wireless and cable segments.

You don't have to use KNX there even if the cable is laid, but by central wiring into the junction box you have everything within reach. [..] If you, for example, lead the wiring of the light outlets to the junction box and also the wiring of the switches, then you can: - Use a normal switch - Use a push button - Use a sensor - Use an automation system

But doesn't that make it even more expensive than relying on KNX from the start? With KNX, at least I can "daisy chain" the push buttons. Having to wire these star-shaped now requires even more cables.

Just a general question to those who reject wireless and believe only "wired" is the way to go (in new buildings):

Do you not have a single (smart) device in use that is connected wirelessly? For example, something like a robot vacuum cleaner or similar, that only runs wirelessly, or am I mistaken? What do you do with the cables that are not installed? Do you retroactively pull in a bus cable there or does it end up being a device wireless after all?

Here one must differentiate. A robot vacuum cleaner and a lawn mower etc. are only a few individual devices which are also uncritical.

In an intelligent building, however, one may have hundreds of devices which then interact with each other and thus seamless communication is essential, and unfortunately, from a certain quantity and distance onwards, the radio systems start to partially interfere with other devices in the system (kind of themselves), adding connection drops and collisions and so on and so forth.

Sure, garden lighting can be realized well, but already the radio connection basement<>upper floor is sometimes almost impossible to realize (with limited means). A cable is simply much easier and less complicated.

Additionally, the radio devices are often an eyesore. For example, in a modern house I want to have as little technology visible as possible. Surface-mounted switches, contacts, actuators, etc. are the complete opposite.

Simply put: Build a backbone with cables and later you could add something here and there on a radio basis. If you build everything on radio from the start, sooner or later you will reach the system's limits. Sometimes faster than you like.

On the other hand, if you only plan to automate a little and leave it at the level of a model railway, you can of course do everything on a radio basis directly. Unfortunately, it still happens quite often that manufacturers give up one or the other radio line after all. So careful preselection is necessary here. With cables it's simply easier.

What do you do with cables that are not laid? Do you retrofit a bus cable there or does it end up being a device via radio after all?

That almost never happens. Because the cables are laid. Otherwise, either poor planning was done (or experience was not listened to) or it was planned in advance anyway and cable pulling is still possible (which is then highly likely).

Name one or more examples where cables might not be laid. In advance: garden etc., that goes relatively quickly.