nostrbounties.com, but I don't like it, too many bugs.
There was a new one nostr:nprofile1qqsxrxhk5c9nlex8xw4v5psu2gkvn370rkr77nys37kvtmvnd5aa7gcpr9mhxue69uhkummnw3ezu7n9vfjkget99e3kcmm4vsq3camnwvaz7tmwdaehgu3wvf5hgcm0d9hx2u3wwdhkx6tpdsqs6amnwvaz7tmwdaejumr0dslhvd7x mentioned some days ago, but I don't know if this is the right approach. Maybe we should just use a #bounty tag.
Discussion
Are bounties posted using nostr? By this I mean is there a note/event/kind standard?
This was all I could ever find on it:
https://github.com/diamsa/nostrbounties/blob/master/EventStructure.md