Comment by somerandomqaguy

.... ?

Windows and many Linux distros by default enable the privacy extensions on the link local address; it's randomized for a period of time. This is right off a Windows 10 VM:

ipconfig:

  Link-local IPv6 Address . . . . . : fe80::9aaf:a280:d593:db1%2

Notice that there's no ff:fe in the middle of the address?

RHEL 9:

  [user@localhost ~]# ip addr | grep fe80
    inet6 fe80::3544:fe14:5cf:5ad9/64 scope link noprefixroute

Fedora Core 35:

  [user@fedora ~]$ ip addr | grep fe80
    inet6 fe80::7752:d2c6:82c3:482c/64 scope link noprefixroute

Ubuntu 22.04:

  user@ubuntu:~# ip addr | grep fe80
    inet6 fe80::5ffe:c565:9de2:58f8/64 scope link noprefixroute

I don't have a Debian right on hand but IIRC they do the same thing. Alpine uses EUI64 I think though.