Up to now every IP65 library contained exactly one Ethernet driver. In scenarios without strict memory limitations I might however be benefitial to have an IP65 library containing all Ethernet drivers available for a given target.
The Ethernet hardware detection that was already present before is used in this scenario to try to initialize one Ethernet driver after the other until one succeeds. If all drivers fail to initialize the user gets informed as usual.
The WIZ811MJ driver was primarily introduced for orthogonality reasons. There are however at least two W5100-based prototypes for the C64 so it makes at least some sense. The name was chosen as sort of placeholder for "something containing a W5100 chip".