I have the same question as you. Two sources of potential feedback I've found, which are not spammy or unpleasant for people:

- Adding an update to an Indie Hacker product profile with a link to a blog post

- Adding a post to the "Share Your Startup" thread in r/startups, which has been a thread that is started on the first of each month [0]

But, in general, I have the same questions as you, so I don't imagine this will provide more than a small boost in feedback.

[0] https://www.reddit.com/r/startups/?f=flair_name%3A%22Share%2...