The system that Umbrel runs on is Debian 12 (Bookworm) without a desktop gui. Umbrel is what is called a Docker desktop. But to move any active system folders on any Linux system, you have to be booted from a USB or CD rom to copy folders it locks when that system is active.
The Umbrel/Debain install they have don’t give you much room to install the desktop GUI other than the x-windows kiosk which is fine if you needed to use that instead of the web address. I extend that drive so I can run a full Linux desktop and programs.
You could go a different route, and copy the /home folder it mounts. If you just want to just expand the Umbrel Docker, but I would recommend formatting the new /home drive in LVM so you can expand it later. I copy and expand the whole docker system because mounting the 1TB drive in home is only going to get you 1TB to install for programs. Which /home directory is used to install user programs in Linux and the blockchain you want to install will instantly fill 65% of that drive (680GB plus database and program).
Lets look at the default install for umbrel:
/dev/disk/by-partuuid/14a31e9d-a8d7-4da0-9eb2-f268dd9d7ad9 /boot/efi auto defaults,sync 0 0
/dev/root / auto defaults,x-systemd.growfs 1 1
/dev/disk/by-partuuid/d1d36e34-2753-4dc7-96eb-3c9b5584e867 /data auto defaults,x-systemd.growfs 0 0
/dev/mapper/umbrel_vol-umbrel_docker /data auto defaults 0 0
# entries kept from original fstab
# <device> <dir> <type> <options> <dump> <fsck>
/ /mnt/root none bind 0 0
/data/umbrel-os/var/log /var/log none bind 0 0
/data/umbrel-os/var/lib/docker /var/lib/docker none bind 0 0
/data/umbrel-os/home /home none bind 0 0
/data/umbrel-os/var/lib/systemd/timesync /var/lib/systemd/timesync none bind 0 0
So when you boot the computer with a live linux usb, (which I use Ubuntu for this so I have all the disk tools preinstalled on it) I launch Gparted, partition and format the 1TB drive, then mount the /data partition of umbrel with the file manager (which is going to be the largest unmounted partition when you exit out of Ubuntu’s setup and go to the live desktop), then copy /data/umbrel-os/home to the 1TB. Then either move /data/umbrel-os/home to a different folder like /data/umbrel-os/home_old and make a new /data/umbrel-os/home or delete the contents of /data/umbrel-os/home so its empty so you can mount the 1TB drive there. Then find the 1TB drive’s UUID with sudo lsblk -f , mount the Debian Linux partition on the Umbrel install (about 4Gb) and edit the /etc/fstab,
Then reboot.
This process is similar to moving a Linux OS /home, however, with a docker desktop /home you have to boot a live linux and move the home folder because the web desktop has to be not running which this one is installed in the /data/umbrel-os/home/umbrel/umbrel/home/
LVM isn’t really a raid. You could simulate a software raid of sorts, but the difference between hat and a RAID, software or hardware, there is automation for swapping in redundant drives/partitions if they go out. LVM alone doesn’t do that.