I want to build a newsletter, help me with ideas 💡

I'm subscribed to a lot of amazing newsletters targeted at makers/founders/entrepreneurs, and I'm even a PRO user of one of them (shoutout to Micro SaaS Ideas!). This inspired me to think about creating my own newsletter targeted at the same segment, a great opportunity to build something that's fairly low maintenance, can be 100% outsourced, and that people would be willing to pay to Premium if the content is crazy good.

But I'm having trouble deciding the theme. What type of content are founders and entrepreneurs most interested in consuming? What are the subjects that you consider valuable enough to pay for? Would love to hear different opinions and ideas.