Installing Ubuntu Server 23.10 (or any Ubuntu distro) via a USB installer, configuring it securely, and setting up various services can be a multi-step process.

Below is a step-by-step guide to help you through this:

Step 1: Create a Bootable USB Installer with Terminal

Download Ubuntu Server ISO:
Visit the official Ubuntu website and download the Ubuntu Server 23.10 ISO.

Insert USB Drive:
Insert your USB drive into your macOS machine.

Identify USB Drive:
Open Terminal and type diskutil list to identify the disk number assigned to your USB drive.

Format USB Drive:
Format the USB drive using the following command. Replace diskX with your disk number.
diskutil eraseDisk FAT32 UBUNTU MBRFormat /dev/diskX

Create Bootable USB:
Use dd to create the bootable USB. Replace /path/to/ubuntu.iso with the path to your downloaded ISO and diskX with your disk number.
sudo dd if=/path/to/ubuntu.iso of=/dev/rdiskX bs=1m status=progress

Eject the USB safely using diskutil eject /dev/diskX.

Step 2: Install Ubuntu Server 23.10

Boot from USB:
Insert the USB drive into the server machine and boot from it via boot manager (normally accessible via F12 on your keyboard) and selecting the appropriate USB.

Install Ubuntu:
Follow the on-screen instructions to install Ubuntu Server 23.10.

Note: due to using a 1440p display, the displayed inferface supersampled to above 4k due to a quirk, so I had to modify the GRUB Boot Parameters when beginning the install to have a usable display.

This can be done by:

Access GRUB Menu:
Once you boot from the USB, you should see the GRUB menu with options like “Try Ubuntu” or “Install Ubuntu.”
If the GRUB menu doesn’t appear, try pressing Shift or Esc during boot to bring it up.
Edit Boot Parameters:
Highlight the option you want (usually “Install Ubuntu Server”) using arrow keys.
Press e to edit the boot parameters.
Modify Boot Parameters:
Find the line starting with linux (it might be quite long and extend off the screen).
Navigate to the end of the line using arrow keys.
Add the following parameter to set the resolution to 1920×1080:
video=1920x1080
Optionally, you might also add nomodeset to prevent the kernel from setting any mode that is not specified in the video parameter:
nomodeset video=1920x1080
Boot with Modified Parameters:
Press Ctrl + X or F10 to boot with the modified parameters.
Proceed with Installation:
You should now proceed with the installation with the resolution set to 1920×1080.
Follow the on-screen instructions to complete the installation.