you'd typically sign on an offline, airgapped computer
it’s not really paper keys then, but yeah i think the best solution for normal people is to just get a spare mac and use it as your hardware wallet.
You could treat them like bearer bonds. Split your holdings over multiple (like tens) of addresses. Sell individual addresses for cash. You'd need to do this via a trusted intermediary who could accept the cash and verify the address before making the exchange.
And yes, this is somewhat absurd. But so are online transactions that can be hacked with no backsies.