If you’re running Sequoia with UTM VMs networking might not work all of a sudden.

The problem is that, for some reason, the new release of MacOs has reset settings of the packet filtering.

Check if it has the correct value (should be 1):

# Check if packet forwarding is enabled
sysctl net.inet.ip.forwarding

Otherwise set it correctl:

sudo sysctl -w net.inet.ip.forwarding=1