Have you done cold outreach ? Is it effective for indies?

I have been playing with cold email outreach for Flezr NoCode Builder

If you are talking about one time cold outreach by simple sending email, DM etc - it hardly works. In most cases, cold outreach needs a sequence of emails to be sent with about 5-6 emails with a gap of 2-5 days. There are hundreds of guides available with templates, best time etc.

But yes, for some products, cold email out reach is a good fit.

Cold emailing is a great way to identify prospects, build relationships, and ultimately close deals. If executed correctly, cold emails can generate leads at a much higher rate than other types of marketing tactics.
The idea behind cold emailing is simple: send out a personalized message to someone who has expressed interest in your company.

For cold email outreach, I'd recommend checking out instantly's playbook. You can check it out from here: https://help.instantly.ai/en/articles/5975326-instantly-cold-email-strategy

This is a great place to kickstart your cold email campaigns

I have been trying cold outreach on reddit for the past 2 days. My target audience is college students who have trouble getting courses or professors they want.

So far it hasn't been successful, but I think it'll work in due time.