ZoneMinder Forums

I have v1.32 on Debian Buster
from the repo deb http://www.deb-multimedia.org stretch main non-free

The Debian 10 Buster with Zoneminder 1.34.x from ZM Repo instructions state
"If you are doing an upgrade I strongly recommend you check the Zoneminder-1.34 Forum area for recommendations from others."
but I cannot find any recommendations on this forum.

Can anyone offer advice?

You apparently did not search very much, as there are a number of posts here regarding upgrades.

In any case, just try to upgrade, and then when you come across an error, search the forum, or post in this thread.

Most importantly, take a backup of the DB before you upgrade. wiki.zoneminder.com/MySQL

The common things I've seen are:

* needing to disable old php, and enable the new php
* permissions for www-data in /usr/share/zoneminder/www not set correctly
* db requires multiple calls to zmupdate.pl
* a2enconf zoneminder was required again
* and one time I just uninstalled, then installed again, as the repos were mixed up.

Worst case you have to uninstall ZM, then install, restore the DB to mysql, and run zmupdate.pl.