One data point, at least: I recently tried to install 5.5 on a system with
two late-model e1000s, and it failed to recognize them. The 2.2 kernel
only supports early revisions of the e1000.
The 2.4 kernel which is used in 5.6beta2 looks to support newer versions
of the e1000, but I haven't tried it with one myself.
Cheers,
--Rich