Welcome in Openshift world 
GNUPGHOME environment variable is set to /var/lib/passbolt/.gnupg but you cannot use this PATH because of openshift restrictions. And if you try to set another path (/var/www/,gnupg), there is chances you cannot write into because of some hardening done in rootless image.
There is unfortunately no immediate solution, as a custom passbolt docker image has to be built to run it on openshift.
As I already worked with openshift, I started a passbolt distroless side-project (link here) with these restrictions in mind but there is some remaining stuff to do to make this work with openshift.
passbolt is a all-in-one image with nginx, php and a cronjob included, I guess separated nginx and php containers are also required for openshift.
Cheers,