Where do I find buyers for a digital product?
Updated
Find the problem, not the audience
Find buyers by searching for the problem, not the audience. Take the exact words someone would use to describe the problem your product solves, search that phrase, and read what comes back. The forums, subreddits, Discord servers and groups on that first page are where your buyers already are.
Do not look for "people interested in productivity". Look for people describing one specific frustration.
The places that reliably work
Subreddits and forums for a specific job or hobby. Discord and Slack communities for a tool or a trade. Facebook groups for local and hobby niches.
Professional associations and course cohorts, if your product is for a job.
Turn up before you sell
Answer questions for a few weeks. Be the person who is helpful about this specific thing.
Then mentioning that you made something is welcome rather than spam. Skipping this step is why most attempts get deleted.
Keep a list
Every buyer’s email is worth more than the sale. The second product sells to that list on day one.
Start collecting emails before you think you need to.