The UGreen NAS runs some type of custom debian OS underneath the hood. Before I totally mess it up by installing my own stuff on it, I wanted to make sure I could restore to a workable state at a later point. On various user groups, people suggested just buying a second NVME to use with other OS's, however, another option is to just make an image of the NVME and in the worst case, just restore to that. Here's the steps I used for that (assumes you have SSH access already setup).
1. SSH into the nas
2. ls -la /dev/disk/by-path
We're interested in the NVME (with all of it's partitions, so we're going to use `pci-0000:55:00.0-nvme-1`)
3. use dd to image the NVME to my home directory: `sudo dd if=/dev/disk/by-path/pci-0000:55:00.0-nvme-1 of=/home/jason/nvme-backup.img status=progress`
Then if the worst happens and we want to restore, we just do a reverse of that and swap the if and of params.