Correct - that was my first try. And with the other installation (Renderer-PC), it works fine, i.e. the certificate was generated automatically.
Then, I tried to install MC30 on my Controller-PC and as I clicked on "Activate SSL", MC says, now I have to generate it by myself?!
By the way: The Media Network configuration means, it should be not only possible but also easy to install the 3-PC-solution (Server-Renderer-Controller), but it's definitively not! I can't understand, why each PC needs an own SSL certificate in this constellation, because it exist only one (!) server, the other PCs use the network, but only as clients. So it's not understandable, why each PC needs an own key with the same software - for shure I'm not the only one who would like to see a kind of automatic configuration.
Despite that, the abovementioned chain is not really practical. With 2 PCs, I can start the server without using the TV and PC-keyboard. With 3 PCs, I have to use them, since MC loads every time it starts the local (Main) Library and the user has to switch manually to another one. There is no possibility to save the configuration or even to configure, that MC loads always the last or a certain library.
Therefore it seems that I have to switch backwards to the 2-PC-solution. But then, I have to synchronize and save 2 Main Librarys from time to time (from the Server and the estimated "Renderer"-PC as also a server for my Controller-PC).
Another possibility would be, that MC installs the Main Library not only local but also on a network drive (from a File-Server/NAS - by the way: thanks to Jim, as he said, instead of a NAS I bought a complete fanless PC as a Server). Unfortunately, with the actual installation process, this is not possible, too.
Finally, it's really important to have touch-/pen-scrolling on MCs Main View like it comes with the file explorer in Windows 11 (or with Gizmo an an Samsung Tablet). Very nice is on the Samsung the Pen-Over-function: Hold the Pen over the cover of an album and you can see the complete album title without need to tap it! Since the titles of classical albums can be very (!) long, this is really practical in a huge collection.