A couple of times, i have got private translation bounty requests that not listed on bitcointalk. i think there are several bounties like this, not official listed on bounty thread but profitable for hunters.
For example, telegram managers for a good project, they earn stably by managing telegram. however, we cant find those bounties in ordinary participation only. Exactly private bounties.
I think that there are not a few examples like this.
and I want to hear about private bounty experiences you joined.
To be honest,I believe that even now we can earn efficiently through this industry.
Check this list
https://icodrops.com/bounty-list/ and some of them have made their own site to run the bounty campaign privately, some may create an announcement in bitcointalk to attract more participants. Private bounty can be searched through joined in the telegram group directly and it will not massively published by the developer. that's the difficult part when we are interesting to join in the private bounty.
Looks like these ICODROPS guys only curate a listing of ongoing ICOs and bounties but they do not manage the campaigns themselves