Ubisoft Connect gives the error "Connection lost: A Ubisoft service is currently unavailable. Please try again later.", which means you cannot get into the game if their servers haven't connected on this install before.

To fix this I simply ran:

echo net.ipv4.tcp_mtu_probing=1 | sudo tee /etc/sysctl.d/custom-mtu-probing.conf

This enables MTU probing which, after a reboot, enabled Ubisoft Connect to connect to their servers.
 
Since it has now connected once, if one wanted to reverse this change, they could run:

sudo rm /etc/sysctl.d/custom-mtu-probing.conf

Besides Ubisoft Connect errors, the game runs perfectly fine.