I had a look at T5965 and several discussions on the forum.
It seems as though under certain circumstances there will be no answer from DHCP even though I can see the DISCOVER being sent out the wwan0 interface, but the connection works if I setup the parameters that can be betrieved from ModemManager.

I am not sure if this a driver problem.

I do have similar problems with a VyOS VM inside Proxmox.

Works fine on latest rolling, thx!

I would very much like you reconsider classifying this as a bug if not security issue.

It does work (eth0 is actually my management vrf interface) if I put the IP for downloads.vyos.io into my /etc/hosts (I guess using a vrf for outgoing DNS requests would be even trickier but this workaround is okay for me, especially since I have a local update mirror reachable via static IP):