You do also need to keep in mind that you need to make sure the ads themselves aren't serving tracking garbage or outright malware, even if you do not offer precise behavioral targeting or even store behavioral data.
You can maybe also sell fun premium features like Discord does with Nitro.
Premium things is something Snapchat tried out for a bit with bitmoji, though to be honest I haven't looked deeply into any available data on how that worked out for them.
1) Free with ads that may be targeted to varying degrees.
2) Paid, with zero ads and zero data collection and zero targeting.
I expect you'd find that there is a significant segment of users who would be willing to pay for the service in order to not be targeted with their specific characteristics and use patterns. Brands can build trust, perhaps make that an objective to support subscription sales.