System administrators can customize many different aspects of Firefox on their organization’s computers using enterprise policies.
This includes restricting access to advanced user interfaces (e.g. blocking about:config), changing the homepage, predefined bookmarks, locking preferences, and even installing custom trust certificates.
This works for the deb packages of Firefox as well as for the snap. In both cases, policies are expected to be written to /etc/firefox/policies/policies.json.
Note that at the time of writing, work to enable this in the snap has landed upstream but due to tight coupling between the release cycle and publication of the snap in the store, it won’t be available before Firefox 91 (due for release on 2021-08-10). The change is also expected to land in the corresponding ESR version (78.13).