I couldn't care less about Bitcoin's use of SHA-256, but based on experience:

First of all, it's quite unlikely that this is going to happen at all. There are no signs of significant weaknesses in SHA-256.

But if it's going to happen, in all likelyhood, you'll get preliminary results long before any actual breakage. (For both MD5 and SHA1, you had around a decade of warnings between "this looks insecure / broken in theory" and "we now have an actual collission".) Anyone paying attention and moving away from algorithms already known to be broken was unaffected by the MD5/SHA1 weaknesses.

Of course, there will be those who will wait until an actual breakage, and a few years more, before they act. (As we've seen particularly with MD5.)

With the current compute density of Bitcoin (which now runs mostly on purpose-built hardware) it'd still take longer than the universe has existed to find even one collision and the actual process of computing SHA256 is simple enough that we're not likely to find a shortcut.

The article is about stablecoins, which mainly live on smart-contract-enabled blockchains (ie, not Bitcoin). I don't think there are many (if any) major smart contract chains out there still using PoW, which I assume your concern is about. Solana's PoH also uses hashes, but I'm not sure what kind of threat that would be (would probably depend on the exact nature of the 'breaking'). Most other major chains such as Ethereum use PoS. The bigger concern would be breaking the asymmetric cryptography those chains use. That would absolutely kill the protocols in their current form (but could probably be fixed by switching to a different crypto standard).

We may never find out. The financial incentive to keep it secret is too great.

If someone broke SHA-256, they could generate blocks directing all coins to their own address and thus destroy the entire system. However, in that scenario it is likely that everybody else would roll the chain back to before the break and restart it with a different algorithm (likely SHA-3).

In summary, an obvious compromise would get caught and neutralized.

So a wily possessor of an SHA-256 break would use it subtly. Most likely they would target “lost” coins that haven’t moved in decades that nobody will notice are missing. Not Satoshi’s though. Too much heat.

If the person who breaks it keeps it secret they become very rich or if the method becomes public then bitcoin quickly crashes to be worth $0 per bitcoin. I don't know if bitcoin could migrate to a different hash if the flaw as disclosed to them first.

Fundamentally, just one update to the protocol (becuase code kind of is actually law, insofar that code is overseen by a group of humans capable of collective action and coordination around documentation and if-then statements) will circumvent any concerns about that particular bugaboo.

If someone broke SHA-256, a lot of modern crypto is broken. I would worry about all of your sensitive accounts like your bank, government before worrying about cryptocurrency.

Much worse things than fraudulent cryptocurrency transactions.