How will you configure OSPF config for IPv6? are you going to configure interface level with neighbour link-local address right?
what is the requirement here to block link-local address?
Note: I may be misunderstood the question here.
the question is:
An engineer decided to secure IPv6 environment with traffic filters and blocks all link-local addresses. What will happen to OSPFv3?
from a CCNP Route 300-101
OSPFv3 needs link local connectivity in order to establish an adjacency. Without it, it will not come up.
If you block all link local then off course ospfv3 neighbors will go down. Since link local addresses are not routeable so I don’t really see any reasons to block it. No only ospfv3 but you will also block neighbor discovery packets which provides basic ipv6 functionality.