- Search for online app directories like product hunt/indie hackers and put your app entry.
- Search for relevant reddit forums, become a member, start answering questions related to your product and add a link at the end.
- Same a last one. Add a post with lot of content of how to solve a problem that community faces and then add your product link.
- On Twitter join the indiehackers/build in public community. Regularly post your updates/screenshots. Engage in community.
- Write a ebook related to you domain. Create a landing page to collect email to deliver ebook. Mention how users can solve the problem by just using your app. Create ads to market the free ebook.
- Split ebook into smaller tweets/reddit post and regularly post them.
- Cold outreach to member on reddit community and ask for app review.