If you mean for Reddit, you’re on one lol

If you mean for Pinterest, it depends on what you need out of Pinterest. If you want a federated social media for images then Pixelfed might be what you want. Karakeep and Pinry are much closer from a user experience perspective, but they seem to me for personal usage rather than a social one, though I can’t say for sure because I’ve never used either.

I think, it is web only but Bowrd.eu https://codeberg.org/bowrd/bowrd

Reddit or pintrest?

There’s quite a few alternatives to Pinterest, but many are just bookmark managers (like Pinterest is anyway). Pinry is probably the closest one to Pinterest.