Installation, setting up IoBroker - still "configurable" at an old age?

Which DIN rail PC are you planning to use ?

The simplest way nowadays is really Alexa and compatible devices. For me, however, it is more of a hobby. That's why I also use ioBroker. It has been running stably for years now. Only the SD card on the RPi worries me. :)

I have, as I think, good to very good knowledge in the sector (e.g., I program as a hobby).

No offense, but I fear there is no one who has good to very good knowledge across the entire IT sector. Programming is one thing, system administration is another, network administration is something else, hardware development is again another, and so on... And each field has several subcategories that sometimes have little or nothing to do with each other. Just because someone can get by with their Windows/Office or, say, a router/switch/access point/NAS, that doesn't mean they have an easier learning curve in projects like ioBroker, OpenHAB, FHEM, etc. But you probably know that by now. ;)

I wonder: Why ioBroker? In such situations, I first try to inform myself about what the solutions can do and which ones might be suitable for me. That also includes basic information about architecture and installation. ONLY THEN do I decide on one and start to try it out myself, preferably in a container, because that is usually already rudimentarily functional. Of course, this only makes sense if I am familiar with containers; otherwise, I have directly opened a second can of worms.

If you just mess around, it can also have some entertainment value, but the potential for frustration is understandably much higher if you expect quick results.

Only thoughts and IMHO:

In my eyes, this is the big problem with all these (software) solutions. They often get in their own way and a lot of background knowledge is necessary. Not just programming skills but also rule algorithms, etc., which is basically a science in itself.

In the end, everyone invents their own wheel to invent a wheel...

...but for a third party, it is then only partially comprehensible, because possibly the world has already moved on and the instructions are then already outdated, as the OP also describes.

Alexa and compatibles is of course child's play, let's not kid ourselves. It's simply an attempt to collect even more data about the users under the pretense of uniting affordable remotely controllable devices under one roof so that you don't have to deal with dozens of apps or physical remote controls.

No offense, but I'm afraid there is no one who has good to very good knowledge of the entire IT sector. Programming is different from system administration, which is different from network administration, which is different from hardware development, which is different from ... And each branch has several subcategories again, which sometimes have little or nothing to do with each other. ...

That's exactly right. Fortunately, we have nearly everything covered within the company, the rest is just "done that way". If it weren't additionally a hobby/pet project of an employee (completely overqualified for such a thing!), we (especially I) wouldn't have agreed to implement it that way (ObenHAB ...)
https://www.hausbau-forum.de/threads/offenes-smarthome-system-prototyp-fuer-jedermann.36275/post-429950

Which DIN rail PC are you planning to use ? ...

see link a few posts above ...

Without having read everything yet, I can still recommend Home Assistant to you. Installation (with experience in VMs) took about 15 minutes. I previously experimented with ioBroker and afterwards with Edomi for my KNX visualization/logic engine. I discarded ioBroker relatively quickly. I still find Edomi (purely KNX!) great, but also the most complex. Home Assistant is the perfect middle ground for me. There are many plugins, the UI looks good, mobile app, and so on.