Set up headless Ubuntu Server x64 on macOS using UTM

Create UTM Virtual Machine

Emulation (Not virtualization)
Hardware: x86_64
Directoruy Share Mode: VirtFS (https://docs.getutm.app/guest-support/linux/#virtfs)
Network Mode: Emulated VLAN
Port Fowarding: TCP 22:22
CD/DVD: Download the ISO of Ubuntu Server x64 (https://ubuntu.com/download/server)

Step 1: On macOS host, Test password authentication

ssh ubuntu@localhost

Step 2: On macOS host, copy public key to Open SSH Server

ssh-copy-id -i ~/.ssh/id_ed25519 ubuntu@localhost

Step 3: On macOS host, test SSH key-based authentication

ssh ubuntu@localhost

Step 4: On Ubuntu guest, verify authorized_keys and disable password authentication

cat .ssh/authorized_keys