So really it was a bug in the alx driver - there was a wrong call order on resume.
Jakub Kicinski has fixed it in the vanilla kernel: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=a4dcfbc4ee2218abd567d81d795082d8d4afcdf6 More details are available in the kernel mailing list: https://lore.kernel.org/netdev/CAJH0kmw00RHaKXqxRFi-7aSj2waYaMBYpp3v1fnC-=237be...@mail.gmail.com/T/#t This bug report can be closed now. Thanks Zbynek
