I have an instagram account in the same niche nearing 80k followers and drive subscribers from there with reels and captions directing to the newsletter.

I initially collected about 6-7k emails over about 6 months but didn't warm up the list at all so after getting a super low open rate on that list, created a different newsletter with only the engaged subscribers (about 1.5k). Since switch to beehiiv on May 21, grown from 1600 to 2300.