Migrating Single Disk to Raid Mirror on ubuntu 20.04

Summary. This procedure is based on my own personal desktop installation of ubuntu 20.04.2. I had a single disk installation containing the following partitions: EFI, root (including boot) on an nvme drive. My goal was to obtain a second nvme of the same make and model, and, migrate to a mdadm Raid installation without backup and restore. In searching, I found many tutorials were quite old, nothing recent and some things have changed since those older tutorials were written.