Honestly, dating apps are one of the cases for a federated system. Use whatever frontend you want, no one person owns the backend so they can’t sleazily monetize you. Probably would need to be a bit more cryptographic than something like lemmy or mastodon though.
With activityhub gaining traction, I actually think it's possible. You essentially self host your profile, which gets federated around. You swipe left/right, thereby accepting federation from a match of blocking.
Depends on how it is used. But I don't think it should be used for the matching process itself though. Maybe to help match interest (tags) between each other, like giving a connection score between two of them, but other than that, I see no other privacy respecting way to use that.
Moreover, on which data would we train on? I don't think there is any anonymized dating app dataset around.
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