Ran the 18.04 beta on Pi3B+ over the weekend and had only one issue.
Had issues with connecting to system via ssh from various clients.
Installed ssh server via the Software Boutique after booting and failure then removed via Software Boutique.
Installed ssh server via raspi-config and had same failure.
Finally ran sudo apt purge openssh-server and sudo apt install openssh-server and was able to connect from all clients that it was failing from before.
Was able to confirm that these clients could ssh into an x86-based 18.04 MATE system.
This is obviously a beta and this is an FYI