So, I was able to create a bootable USB installer using this -> Option 4.
During live CD session, I create a new MSDOS partition table on the target drive, with the following partitions:
ubuntu-mate@ubuntu-mate:~$ sudo parted -l
Model: ATA Seagate SSD (scsi)
Disk /dev/sda: 500GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
1 1049kB 630MB 629MB primary fat32 boot, esp
2 630MB 1704MB 1074MB primary linux-swap(v1)
3 1704MB 500GB 498GB primary ext4
ubuntu-mate@ubuntu-mate:~$ sudo fdisk -l
Disk /dev/sda: 465.76 GiB, 500107862016 bytes, 976773168 sectors
Disk model: Seagate SSD
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x18fbe4e3
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 1230562 1228515 599.9M ef EFI (FAT-12/16/32)
/dev/sda2 1230848 3327999 2097152 1G 82 Linux swap / Solaris
/dev/sda3 3328000 976773119 973445120 464.2G 83 Linux
Installation seems to go great, but I get the "FOLDER?" message upon startup. I tried to OPTION + COMMAND during boot, thinking I have to manually select the EFI boot device, but that didn't do anything either.
Here are some (animated) screenshots from the installation when customizing the installation partitions.
Lastly, before clicking "Install Now", I tried selecting both /dev/sda and /dev/sda1 (efi) as the device for the boot loader installation. Neither worked. Should I have selected /dev/sda3 (ext4)?