It was asked a couple of months ago, but given the AI enshittification, it seems a good time to ask again.
I looked around and found:
- Pinetta is/was in development but seems dead with only an alpha release. I am chasing this up on Matrix. edit: Apparently still, technically, active although progress has been slow
- Pinry is a FOSS alternative, but not federated, that seems dormant. However, it works and is in Python, so someone could bolt an AP server to it, he says airily.
If it integrates with the fediverse, it can be promoted on other platforms and doesn’t need critical mass.
That’s the advantage. All the platforms are trying to synergize, not steal from each other like the corporate apps.