Comment 4 for bug 1988069

Yes, the network is still usable since it could be configured some other way (config drive, manually). You can't run IPv6 on it, and it's right near the 68-byte IPv4 minimum.

The other bug you linked about min/max network MTU would be useful here, although there are cases already where you can overflow the default DHCP response size with things like static route options. In the end the IPv6 minimum of 1280 seems a good place to start.

As a reference I tested this on Ubuntu 20.04 with the 5.15.0-46 kernel. Perhaps there was a kernel bug in some versions that triggered the invalid argument? If that is the case then I'm not sure there's a bug here and we can continue discussion in the linked MTU bug.