My problem was solved by removing the other drives, and using the the target drive internally instead of externally. If anyone else sees this, I recommend this solution! Thanks to everyone who helped. :)
I was attempting to install Ubuntu Budgie onto a formatted NTFS external HDD using a USB flash, but I received the "No EFI System Partition was Found" error. I tried installing anyway, but it failed, as expected. I was following this guide: https://linuxhint.com/install-ubuntu-external-hard-drive/ and it didn't mention anything about an EFI partition. How can I avoid this error in future?