There are a few more bounties like this out there.
1. Tenstorrent https://github.com/tenstorrent/tt-metal/issues?q=is%3Aissue%... $200 - $3,000 bounties
2. microG https://github.com/microg/GmsCore/issues/2994 $10,000 bounty
3. Li Haoyi https://github.com/orgs/com-lihaoyi/discussions/6 multiple bounties (already mentioned upthread)
4. Algora also hosts bounties for COSS (Commercial OSS) https://algora.io/bounties