That is something that can be addressed via software update after release.
Firefox already has the setting “privacy.resistFingerprinting” but what exactly that controls I don’t know.
As the original comment says, by its very nature, the librem 5 will be a bit niche and hence to some extent self-fingerprinting. So it is something that ought to be looked at.
Straight off the bat, if the screen resolution is 720x1440 (allegedly) then that is unusual (doesn’t match any iPhone, Samsung Galaxy, google Pixel that I am aware of) and that is not something that you would want your browser to provide false information about.