How do you collect feedback after launching a niche product?

I recently launched a niche product for composers called ShevtoneAudio.

One thing I've realized is that building the product is actually easier than finding the right users and collecting meaningful feedback.

I'm trying to avoid spam or aggressive promotion and instead reach people who would genuinely benefit from the tool.

For those who have launched specialized products:

• Where did you find your first 100 real users?

• Which communities gave you the most valuable feedback?

• Did Product Hunt continue bringing users after launch, or did you focus on other channels?

I'd really appreciate hearing about your experiences. I'm sure many makers building niche products face the same challenge.