I'll definitely check out Prowriting Aid. Thanks for suggesting it! I've never heard of it.
We accept all stories, including prison stories. We ask all writers to keep stories appropriate by not writing about extreme acts of violence, hatred, or overuse of vulgarities.
If you're interested in submitting a story, send it over, and I'll give it a read. I'll let you know what I think within 1-2 days.
Hope this helps!