There’s a few with a paid tier, and a few that charge for the convenience of getting the app from the platform’s store. Threema does this for instance.

samourai wallet has successfully found a way to generate revenue from whirlpool coinjoins, the entrance fee also functions as anti sybil attack and is therefore beneficial for the user for privacy gains

sparrow wallet then implemented whirlpool and takes a cut from from the entrance fee that come from sparrow users

beautiful FOSS in action