Reinstall KDE system with LXQt [1]; KDE network and display configuration extremely difficult with numerous bugs

KDE has some great reputation as a desktop environment in Linux and has won considerable plaudits. It however has numerous unresolved bugs which I have observed in the display and network configurations that are leading me to ditch KDE on one of my desktop computers in favour of LXQt. I have had three computers running KDE and one running LXQt all on top of Debian but I will be taking two computers onto LXQt and therefore only having two running KDE.
The concerning issues that are being observed with KDE mainly concern non standard configurations in both display and network, and also the inability to use x11vnc on KDE which somehow blocks it from running. The problem can be summed up as KDE not being sufficiently versatile to allow different configurations where the standard ones are insufficient. For example the VNC client designed for KDE, Krfb, will only buffer one display on a two display computer, making it inferior compared to x11vnc.
The summary of the issues experienced to date is:
  • Networking. Unable to configure a static IP address and route for a network adapter and stop the automatic configuration of an adapter via DHCP. Unable to disable a network adapter and stop it from connecting as KDE ignores the disable setting and creates another new adapter with the same settings as the disabled one (the only option then is to disable or remove the adapter at hardware level).
  • Display. Unable to save the configuration of two displays on my computer. The displays are stacked vertically. KDE is unable to remember these settings and after each reboot, defaults to side by side displays.
  • Remote Frame Buffer. As mentioned above, KDE stops x11vnc from working. Krfb will only buffer one display in a dual display system.
My networking requirement is special as the computer has two network adapters due to being required to connect with two different networks. On LXQt this is relatively easy to set up. On KDE I have experienced the problems mentioned that it keeps ignoring the manual settings. Only one of the adapters can be a default gateway because there can only be one default route to the internet. I have made it clear that the manually configured adapter will not have a default gateway but KDE ignores the instruction to use the manual settings and keeps sending DHCP requests on that network. The net result is it has become impossible to enforce the required network configuration of the computer. 
To illustrate that this is not difficult on other desktop environments, I have set up a virtual machine on the same computer which is set up in VirtualBox settings with the two network adapters with the appropriate configuration in LXQt (the VM is running Lubuntu). This has worked flawlessly without all the dramas that KDE is creating. The network configuration on LXQt on the virtual machine is implemented as the option “Shared to other computers” which allows the specification of an IP address and netmask without gateway settings. In other words that adapter does not have a gateway specified and must not send DHCP requests on the network.
Another difference between LXQt and KDE with regard to networking is the list of configuration methods and their implementation. In the connection manager that is provided with Lubuntu, which is admittedly different from LXQt on Debian, “Shared to other computers” lets a manual IP address and netmask be specified. But this information can’t be put in when selecting the same configuration method in KDE. The KDE network manager in this case automatically creates its own IP address on the 10.x.x.x network and you obviously have to configure the rest of your network to match.
The key problem with KDE is it takes over too many things in a computer and makes it difficult to work around its default settings. In LXQt it is extremely straightforward to configure a non standard dual display and save the settings in a config file, extremely straightforward to install and manage x11vnc and it can be more straightforward to configure a network adapter. However ConnMan is a bit more tricky to configure than the Lubuntu network manager – the Lubuntu one is one of the best ones I have used on Linux overall.

I have started a complete reinstall of Debian 10 on the computer despite my misgivings over having to reinstall all the software (including the tricky iscan software for the Epson scanner), because KDE has such an impact on the system, that it is difficult just to put LXQt over the top of it.