I was trying puzzle number 68 before it got solved. With https://github.com/brichard19/BitCrack

But it makes no economic sense. I did the numbers for a RTX 3090 and the expected return was about 1/100 of the prize. So even if a pool could exist, it was not efficient.

And a pool can't exist, because anyone in the pool that finds the key could just claim the prize for themselves (unlike in mining).

The closest thing to a pool is https://btcpuzzle.info/ where explored areas are marked as “key not here”.

Have you had a go? 

There must be some people using GPU's or LLM's on this stuff by now.

bitcoin

Bitcoin Puzzle - PrivateKeyFinder.io

Yes. That was puzzle 68 or 69. But until those, no puzzle was solved for two years. And it's amazing, because the puzzle number is the number of bits of the private key, and a 71 bit private key with 6 BTC has not been cracked yet.

12 word mnemonic is 128 bits key, and complexity doubles with each bit.