So, use git?

What if say you bribe someone who can somehow get access to the files and modify them?

What if say you bribe someone with access to the private keys to append a false entry?

Indeed, you must have a Chain of Command/Chain of Trust that the majority of people will trust. I believe there are ways.

So what's the advantage over using git?

1 extra level of security? Perhaps the added cost of the system doesn't warrant it, perhaps there are better ways to mitigate.

I'm not an expert in the area and don't know the nuances as much as I'd like, like I've wondered if there's a way to have 2 keys - so in the case of blackmail, you give a different key than normal, which will work - however then there's a way to trace.

Obviously the best system is having a system of governance that is stable and accountable. The situation to perhaps design for is say tyrannical dictatorships that may rise.

I suppose the most important aspect of git would be redundancy of data, along with perhaps immutable and/or offline archives; evidence may be changed without anyone ever knowing though to check, unless perhaps there were regular (every 5 years?) consistency checks between archives and present-day/online historical data?