Backstory: News aggregation is huge. There are so many websites out there with information (and clickbait) that it's hard to sift through the noise (clickbait). A niche that I've stuck in for the past five years is boostrapped entrepreneurs.
/ˈbo͞otˌstrapt/ - To finance your company's startup and growth with the assistance of or input from others
The Idea: A magazine designed solely for boostrapped entrepreneurs.
Deep Dive: Given this niche it makes finding content very easy in the respect that you are laser focused on that specific content but it's not a hugely popular space. One of my favorites is Rob Walling (https://robwalling.com/) who co-hosts startups for the rest of us (https://www.startupsfortherestofus.com/) a podcast aimed directly for boostrapped entrepreneurs.
You should develop a script for interviews and try to interview anyone you know in this space.
Validation: foundr is a bit broad but Nathan Chan has built quite a successful business in this space.
Monetization: Once you get 10-20k subscribers you would be able to sell advertisements. Additionally you could sell premium content for a monthly subscription.