Hello,
Today I learned about dm-vdo as an alternative to ZFS/Btrfs for file system deduplication and compression, it works with LVM which Qubes OS default installation uses.
https://docs.kernel.org/admin-guide/device-mapper/vdo.html
Maybe it’s a good system to be able to compress qubes and even if you create a bunch of similar templates or standalones it doesnt take your whole disk…?
Regards