I’m a longterm Gentoo user looking at Calculate to recommend for others. udev now seems to have either aligned with or joined systemd which I regard it as an unnecessary and badly-designed modification of a critical system component.
I’ve just started building a new installation - something I do every year or two - and found that installing eudev:
emerge -av eudev
was fast, painless and fixed the problems created by udev which was in the original Stage 3 tarball.
emerge automatically removes udev, and I left ‘net.ifnames=0’ in the kernel invocation without generating any error messages.