Here's an example of a Bruen tenet (as taken from the baton lawsuit):

"Bruen specifically  rejects  means  end  scrutiny  and  requires  the government to “affirmatively prove that its ... regulation is part of the historical tradition that delimits the outer bounds of the right to keep and bear arms.”  Id. at 2127."

I have no idea of what the laws were in 1791, but I'd be surprised if every firearm possessor in many given legal jurisdictions (state, county, town, etc.) had to go to the government and give them the serial number on their firearm(s) (and be fingerprinted). 

"Registration" is an anomaly, not part of the mainstream widespread historical tradition (as far as I know). It is still an anomaly today, with the majority of states having no such laws (as far as I know).

Also, I'd be surprised if firearm sellers then had to be registered with the government and keep detailed records of every sale of every firearm, subject to inspection at any time by government agents.

Is there a legal reason "registration" has not been challenged yet? (Or maybe it has been challenged in some jurisdiction requiring registration... if so, could someone please provide a link to the filing? Thanks.)

Many HI laws will take years if not a decade to overturn based on the new SCOTUS ruling.  So be patient.

We already tried to get rid of in person reg, and HI AG has disregarded the judges ruling by requiring out of state to bring the guns in and non FFL sales to bring their guns in for inspection.

What we are all doing is for the next generation of gun owners.