bobzr
I use LVM partitions for my data and backup devices. Of course I need the tools of lvm2 to access my other multi-boot Linux installations.
demm
I also have no clue what you mean by a difference with symlinks. I originally installed KaOS to ext4, and then cloned it to btrfs with a set of predefined subvolumes. The procedure worked with a normal partition /dev/sdax as root, and should work with a logical volume of LVM likewise. /usr is located always on the same subvolume as root. Thus all symlinks should work. I copied with rsync -aHAX, so any symlinks should be preserved.
It is also no grub issue. I used grub from another Linux installation to boot (openSUSE). I recall that I could go to the grub prompt and list all lvm devices, but nevertheless got the error message at boot.
Greetings,
Bequimão