My app got 2k installs on release, purely from 20 organic Reddit posts with 300k impressions.
Here how to find subreddits to promote your app.
All of them allow self promo, but some have additional conditions.
Platform related subreddits. Usually allow self promo on certain day of the week, for active participants(make 5 unrelated posts within a week).
r/iOSApps
r/macapps
r/MacOS
r/apple
r/iOSProgramming
r/appledevelopers
r/windowsapps
r/WebApps
r/WebApps
r/genAIApps
r/apps
indie hacker, builder related apps. They usually do not exactly allow promotion.
But they tolerate link to your app as long as it is related to content of post.
Make about your relevant experience mentioning your app in the process.
r/indiehackers
r/SideProject
r/scaleinpublic
r/buildinpublic
r/GrowthHacking
r/AppStoreOptimization
r/AppBusiness
r/SaaS
r/MobileAppDevelopers
r/iOSAppsMarketing
Niche subreddits. This one is unique for every single app. Finding a subreddit, specifically related to your product is like finding a gold mine.
Even if they don't allow self promo, you can ask users there if they would like app with your functionality without mentioning app itself. It might give you some validation.
They are usually especially enthusiastic about beta tests(for some reason open beta invites are not viewed as ads ).
Paid ads are also can be extremely efficient there.
For me the following subreddits worked:
r/StableDiffusion
r/GenAIApps
r/AIArt