that's not why gold is valuable, historically. Historically gold is valuable because it's rivalrous, fungible, and most importantly, easily verifiable.

You can assess approximate purity of the metal with very low-level technology (https://en.wikipedia.org/wiki/Touchstone_(assaying_tool)). Transactions thus have a lowered barrier of trust. Before gold and money, you could only transact in debt to labor (see debt: 5000 years) or socialized obligations, and to be sure the person would conduct that labor, you had to trust them, or trust society to honor the obligation.

More interestingly in particular, once gold came into being, two people could reliable transact over a very long social distances, (without necessarily knowing each other's reputation). You just had to trust an intermediary party to transport the gold. Nonetheless, that opened markets up considerably.

This is correct. Gold is the original “it’s valuable because everyone agrees it is,” and retains that first mover advantage. Over the centuries there have been numerous challengers. Almost all (silver being a notable exception) failed.

Indeed. That does not negate its base value even in barter. (Though it's much lower.)

And especially items made with the use of gold can get really worthwhile - such as semiconductor chips...

So in a funny indirect way, Bitcoin is tied to gold. Both of which are tied to specific costs of labour. Bitcoin however requires a lot of expensive infrastructure to run to be worth anything. (Esp. networking, required to ensure no fake mined bitcoins are in circulation.)

Even printed cash is better at this.

The whole state is required for printed cash to be worth anything. I doubt it's cheaper in any comparison.

I think just saying "it's only valuable because it's agreed upon" is shortchanging gold. Its verifiability is an intrinsic property if ever there was one, and has to do with quantum relativistic effects in its outer electron shell that only gold has.