More than that, you need a grand conspiracy that is so obscure third party observers can't see it happening. Relatively easy with software, because software is obscure almost by definition. Difficult with something tactile like paper ballots.

(Or you need a country where those third party observers are already powerless, but that's beside the point).

It's easy to hack analog as well if the administration is in on it.

Sure with gerrymandering. I’ve been involved in two major elections in the last 12 months in the uk, one as a candidate. I couldn’t think of any way of significantly changing the votes without another party finding out. Can’t register fake people in bulk, can’t registrr normally non voting people for postal votes without them finding out, can’t vote as multiple people without a lot of co conspirators and without at least some finding out they’d already voted, can’t introduce fake ballots without many conspirators, can’t change ballots or lose ballots

Gerrymandering isn't the only solution there.

If you're the secretary of state for a given state of the union, and you're in charge of the voter rolls, and you're running for office, then you are fully empowered to just remove anyone from the voter rolls who has a name you don't like, or who has a race you don't like, or who has a political affiliation you don't like.

And you can stymie all attempts to uncover your malfeasance by just shoving all those requests in the drawer, where they get mysteriously lost.

I don’t think this would work. Isn’t Georgia in the middle of some lawsuits regarding their elections?

That is not a property of paper ballots, that's just the property of a broken election system.

But that can’t be done en mass without people noticing and reporting it

No, it isn't. You can't be "in on" a properly constructed election system, because all relevant steps are open to the public for any interested party to watch. Which is exactly the problem with digital voting: They can not be transparent while also preserving secrecy of the ballot.