I sould have said (insmod and not lsmod) on my previous post.
I guess I’ve found the problem: the e1000e module in the 18.104.22.168 kernel does not include support for the Intel 82574L. Newer versions of the module do (just checked the original from the Intel support site).
So I will have to either recompile the module with the same kernel somewhere else or replace the whole kernel with a newer version.
Any suggestions of what may be simpler to accomplish?