I found a Firefox ADMX template project on GitHub, though it's third party and entails running a VBS file on system startup, so I wouldn't recommend it.

Most software patching solutions have a way to push files though, and you can use something like this: https://www.itsupportguides.com/knowledge-base/tech-tips-tri...

They are working on it: https://wiki.mozilla.org/Firefox/EnterprisePolicies