You could use group policy.
https://support.mozilla.org/en-US/kb/customizing-firefox-usi...
Re:Firefox Profilemaker
by forapurpose on Monday December 03, 2018 @07:31PM
(#18594676)
Look up Mike Kaply's blog; he covers it extensively and, AFAIK, knows the topic as well as anyone.
This used to be impossible, and essentially made my employer banish Firefox in most cases.