This is a seedling that survived 2021 mild winter in zone 7a without any protection grew well and developed a thick trunk but died to the ground this year after 6f.
I was cutting dead / rotting trunk that was freeze damaged until only a small stump was left. It's now growing buds on the stump!
I have mature Yuzu in a container now so this plant is not worth protecting as it is a seedling, but thought I would report on this finding. If this was a mature Yuzu on its own roots I'd probably try to protect it.