Simple Mindmap tool - How should I monetize?

👋 Hey everyone

I built a free mindmap tool at https://simplemindmap.com a while back and have been hosting it for a while. It gets around 10k - 15k visitors each month.

Now I don't expect it to be paying the bills at that volume, but it would be nice to potentially cover the domain costs, I would imagine the monthly volume might be enough to do that. My only problem is what monetization options are out there.

It seems Google Adense is purely for content sites nowadays so I can't go that route. Perhaps affiliate programs? Although those seem to be targetting content sites like blogs too. Has anybody had any luck putting amazon affiliate links on their apps/sites (as if it were a banner ad for example)?

Are there any non-obvious approaches to monetization? It's clearly not a tool somebody would pay for as it is intended purely as a free to use convenient tool when you want to mock up a mindmap quickly.

I'd love to hear what people think!