Network does not work with latest kernel
I just found out that the latest kernel that is now used in Debian renders the network non-functional. I don't know why this is. I have several PowerPC based computers at home with MintPPC. I am now writing from an iBook G4 with kernel 5.5.0-2 without these issues.
Edit: I found out that kernel 5.7 has the same problem. I thought that on my development machine, which is a PowerBook G4 12 inch, the ethernet port broke down. Maybe it has to do with the kernel I now realise. Maybe the ethernet port is not broken but simply not working because of a malfunctioning kernel.
Luckily, MintPPC installs the 5.5 kernel. So no worries.
The 5.5 kernel originates from kernel source 5.5.17-1:
Ok, it has nothing to do with the kernel. Apparently, the configuration files for the network have changed and this means that ethernet does not work out of the box in network-manager.
The solution can be found here.