Hello,
when trying to backup a lava instance, keep in mind that lava is made of two parts : the server (only one) and the dispatchers (usually more than one).
For the server you should backup:
* the database (see /etc/lava-server/instance.conf)
* the configuration:
** /etc/lava-server/
** /etc/lava-dispatcher/certificates.d
* the job artifacts: /var/lib/lava-server/default/media/job-output
On the dispatchers, you should backup:
* dispatcher config: /etc/lava-dispatcher/
* all the changes you did like, /etc/ser2net.conf, udev rules, ...
Hope that helps.