I have heard good things about substack. In terms of starting to collect subscribers, I would create one useful guide or other pieces of content that people in

I have heard good things about substack. In terms of starting to collect subscribers, I would create one useful guide or other pieces of content that people in this industry are (very) interested in and offer full access if they subscribe to your newsletter. It might annoy people that they must subscribe to get full access, so you can use a more gentle (but less effective) option and that is showing a popup in which you offer them to get a future relevant post (mention the title in the popup) once it's published. You can do some sort of an interactive post in which they get feedback on their entries via email (I created one for evaluating your startup idea). And never, never ever spam people. Oh, to find relevant content people are interested in try ahrefs (paid, but a great research tool).