Took the time to upgrade a router I had with an eapol configured WAN interface using vif 0 from a 1.4 rolling release, specifically 1.4-20230714, to the release candidate. During this reboot, the device failed to boot properly as eth0.0 wasn't yet a valid interface. In the 1.4 rolling release, I was able to rectify boot issues by affixing hw-id, but in this rc, the hw-id seems irrelevant.
I beleive there are some existing bug reports around interface ordering and configuration at boot time, but given this was eapol specific, I wanted to open a seperate bug report here.
The specific service that appears to cause the config to fail here is the dynamic dns client.
Dec 22 18:35:31 sudo[1733]: root : PWD=/ ; USER=root ; COMMAND=/usr/bin/sh -c '/usr/sbin/vyshim /usr/libexec/vyos/conf_mode/dns_dynamic.py'
Dec 22 18:35:31 sudo[1733]: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=0)
Dec 22 18:35:31 vyos-configd[767]: Received message: {"type": "init"}
Dec 22 18:35:32 vyos-configd[767]: config session pid is 1555
Dec 22 18:35:32 vyos-configd[767]: Received message: {"type": "node", "data": "/usr/libexec/vyos/conf_mode/dns_dynamic.py"}
Dec 22 18:35:32 vyos-configd[767]: Interface "eth0.0" does not exist!
Dec 22 18:35:32 vyos-configd[767]: Sending response 2