> Does anyone know other innovative PoW chains?

Wikipedia gives some ideas:

https://en.wikipedia.org/w/index.php?title=Proof_of_work&old...

https://en.wikipedia.org/w/index.php?title=Proof_of_work&old...

For example

* Cuckoo Cycle: https://docs.grin.mw/wiki/miscellaneous/cuckoo-cycle/

* The paper "Ofelimos: Combinatorial Optimization via Proof-of-Useful-Work A Provably Secure Blockchain Protocol": https://crypto.iacr.org/2022/papers/538804_1_En_12_Chapter_O...

Quote from Wikipedia concerning Ofelimos: "At the IACR conference Crypto 2022 researchers presented a paper describing Ofelimos, a blockchain protocol with a consensus mechanism based on "proof of useful work" (PoUW). Rather than miners consuming energy in solving complex, but essentially useless, puzzles to validate transactions, Ofelimos achieves consensus while simultaneously providing a decentralized optimization problem solver. [...] The paper gives an example that implements a variant of WalkSAT, a local search algorithm to solve Boolean problems.|"