What have you tried so far, and what’s the usage like? If lots of people are using it and genuinely find it valuable then maybe some portion of those would be willing to pay for it. Otherwise some type of sponsorship / non intrusive ads might work though it looks like you want to avoid ads.
Check out listen notes [0] for some inspiration. It’s a podcast search engine that is profitable, and the founder has some good write ups on the blog.
0. https://www.listennotes.com/