Data recovery from a dead Netgear ReadyNAS Duo

I found the following pages helpful:

https://superuser.com/questions/1031283/how-to-get-the-data-off-of-a-readynas-drive
https://jim-st.blogspot.com/2012/07/mouning-readynas-drives-on-x86-systems.html
https://technostuff.blogspot.com/2012/06/how-to-mount-disk-used-by-readynas.html

I found that the right-hand drive was mountable, but required installation of some packages on a Fedora 29 desktop system:

git clone https://github.com/alperakcan/fuse-ext2.git
dnf install autoconf automake libtool
dnf install libfuse-dev e2fsprogs comerr-dev e2fslibs-dev
dnf install fuse-libs fuse3-libs
dnf install fuse-devel fuse3-devel
https://fedora.pkgs.org/29/fedora-x86_64/libcom_err-devel-1.44.3-1.fc29.x86_64.rpm.html
dnf install Downloads/libcom_err-devel-1.44.3-1.fc29.x86_64.rpm
dnf install e2fsprogs-libs e2fsprogs-devel

Next steps:

vgchange -ay c
lvscan
fuse-ext2 -o sync_read,allow_other,rw+ /dev/c/c /mnt/tmp

Data now accessible in /mnt/tmp