This same issue with the DUID generation on 25.12 has been happening on my end since my RCs tests. (I know this because, from my understanding DUID-LL is directly related to device MAC, which on my setup now that I’m un-CGNAT I would not have internet access when I bridge the ONT if I clone the MAC unlike when I’m still CGNAT, so the DUID has to be cleared as I’m not cloning the ONT MAC)
If you are using owut you can set it up like what I did:
To add, this can be automated without typing --init-script every time by adding it as option in the /etc/config/attendedsysupgrade file under owut section: option init_script '/rom/etc/uci-defaults/99-asu-defaults' so I only have to do owut upgrade -v
Lastly, others noted that it might require a new assignment from the ISP, but for me it’s not the case so it’s ISP-related since I only need to power off the ONT for at least 3 min (max 5) to get a new assignment and that did not work. Thus I opted to clear the DUID every time.