(A little update)

What I did was:
cp /usr/share/lxc/templates/lxc-debian /usr/share/lxc/templates/lxc-devuan
cp /usr/share/lxc/config/debian.common.conf
/usr/share/lxc/config/devuan.common.conf
cp /usr/share/lxc/config/debian.userns.conf
/usr/share/lxc/config/devuan.userns.conf

I don't know if the last one is used. It doesn't seem to be referenced
in the template.

Then I:
- removed the function configure_debian_systemd.
- changed the MIRROR to https://auto.mirror.devuan.org/merged/
- removed debian from all the function names
- changed debian to devuan in all the messages

Then I created a container the new template.

There were some warnings.

insserv: warning: current start runlevel(s) (empty) of script
`checkroot.sh' overrides LSB defaults (S).
insserv: warning: current stop runlevel(s) (S) of script `checkroot.sh'
overrides LSB defaults (empty).
insserv: warning: current start runlevel(s) (empty) of script
`checkroot.sh' overrides LSB defaults (S).
update-rc.d: error: umountfs Default-Start contains no runlevels, aborting.
insserv: warning: current start runlevel(s) (empty) of script
`hwclock.sh' overrides LSB defaults (S).
insserv: warning: current stop runlevel(s) (0 6 S) of script
`hwclock.sh' overrides LSB defaults (0 6).
update-rc.d: error: cannot find a LSB script for hwclockfirst.sh

These are the same warning encountered with the Debian template. So if
anything we should fix that for Devuan, but it doesn't seem to be a problem.

I then modified the containters config and network settings and it
started and seems to work fine.

Simon