UTM supports serial device emulation through network sockets (QEMU backend only) or pseudo-TTY device. To setup, add a new serial device (QEMU or macOS Apple).

When the virtual machine is started, any serial device (excluding built-in terminal) will be listed in the details and you can use this path to connect to the port.

macOS Pseudo-TTY

The easiest way to connect to a PTTY device is with the screen command:

$ screen /dev/ttys006

In this example the PTTY device was created at /dev/ttys006.