net.ifnames=0 not working with 6.6.67 kernel?

[Darknight]

I've been using net.ifnames=0 as a built-in kernel command line parameter for years, today I upgraded to 6.6.67 and to my dismay I had to boot into a usb stick to go back to the previous kernel, the box was not completing init because of missing eth0. The other built-in paramenter (ROOT=PARTUUID...) works, so I assume the problem is related only to net.ifnames=0 and not the built-in parameters as a whole.
I also discovered that only the first menu entry marked for boot in efibootmgr shows in the bios boot menu.
Have I missed important announcements regarding predictable network interface names?
If so, how can I tell which name is being given to the interface if I cannot rely on eth0 and boot won't complete?

[Hu]

Technically, net.ifnames has no effect on the kernel. It has an effect on systemd-udevd to tell it not to mangle your network interface names. Therefore, my first candidate would be to suspect that in the "bad" kernel, this parameter is not visible to systemd-udevd. What is the output of xxd /proc/cmdline in the bad kernel versus in the good one?

[Darknight]

It seems /proc/cmdline is fine, something's wrong with network interfaces instead. On the surface it seems that they are detected in a different way and this impacts udev rules that rename 2 of the interfaces (now the wrong ones including eth0!).
Thank you for the tip, it helped me find the right direction.