With so many websites banning self promotion, how do you go about promoting your business?

As the title states, many websites ban self promotion (e.g. Facebook groups, Reddit, Slack groups, Discord etc.). Even responding to a Reddit post looking for a solution to a problem that your product solves can lead to a ban or deletion of the comment.

Of course the alternative to this is to pay for ads or build up your own social media following but as someone who is working on a startup while maintaining a full-time job who lacks the time and money to pay for $1.50 to $2.00 ad clicks what other options are there?

Thank you!