So we're seeing this error as well, except Moodle 3.3 seems to want unoconv 0.7. Well and good, but we're running Centos 7 and there isn't an rpm for unoconv 7. So we installed from source, and the testunoconv gadget in Moodle says it doesn't support the version of unoconv we have installed which ostensibly is the one it's supposed to want. It should be findable in the default path /usr/bin/unoconv.
Thanks for any help, much appreciated!
-jason