Yesterday I put in a new SSD and reinstalled Windows and moved the old SSD into a USB NVMe enclosure. I need access to my old WSL1 files and right now this means I am running Double Commander as admin which is not ideal. I'd like to be able read but not write the files on that disk without ruining the special voodoo magic that LXSS does because I'd like to keep the option of just swapping back this disk into the laptop a possibility. Because of this I am not comfortable to just edit willy-nilly the driver permissions because I am afraid it'd recursively set on everything. Also, if it's recursive, it'd take roughly forever even with an SSD with (many) millions of tiny files. So Permissionless external drive with NTFS is a no-go.
Following and adopting the great advice in this comment encouraging me to create a disk image backup, I have used Macrium Reflect to image the entire disk and then set the actual disk aside. Macrium provides access in two ways. One, the image can be mounted after a right click:
and then in the window where it becomes possible to mount partitions from the image, there's an option "Enable access to restricted folders" while not at all changing the image:
The second option is available from the Macrium Reflect application itself. After clicking the Restore tab, it becomes possible to browse for the image and an option is available to boot a VM from the image using Hyper-V:
The only disadvantage of this approach is the increased disk usage -- Macrium uses compression so that helps a bit. Note how the first image shows the file is 315GB while the second image shows it contains 450GB data.