The problem of scale for profitability from ads is certainly there. You could look to use something like admob to start with to make some money back (although the earnings likely will not cover with cost of marketing, without scale). Source: over 1 year ago

1. AdMob Google is the No 1 player in the mobile advertising market. It was already the largest online advertising company when it acquired AdMob. AdMob makes earning revenue easy with in-app ads, actionable insights, and powerful, easy-to-use tools that grow mobile apps. - Source: dev.to / almost 2 years ago

Use online services, such as Google AdMob, for filtering and sorting in-app ads. Source: over 2 years ago

There are different ways to monetize with your Flutter app. You can make users pay to download it, you can have in-app purchase plans, you can let users subscribe using recurring payments to use all the features, or you can show ads to your users. In this article, Dhruv Nakum teaches you how to integrate AdMob into your app. - Source: dev.to / over 2 years ago

Head to https://paywithmoon.com/ and sign up. Source: over 1 year ago

I am the founder of paywithmoon.com. Source: over 1 year ago

Moon might be a good option for you. They offer prepaid, non-reloadable debit cards that are paid for in BTC. Best of all, there’s no KYC at all, and they can even be added to Apple Pay or Google Pay. I quite like it, I think it’s pretty neat. Source: over 1 year ago

3) As a last resort, there are tools to make sats to fiat payments, like https://allark.io/ https://paywithmoon.com/ or https://www.coindebit.io/. Source: over 1 year ago

Use paywithmoon.com to create virtual Visa card(US merchants only!) Use bestchange.®u to exchange rubles to Bitcoins and send them to Moon. Source: over 1 year ago