What is Mistpark?
Mistpark was the name of two different roughly Facebook-like Fediverse projects.
The first Mistpark is now known as Friendica; see there.
The second Mistpark, Mistpark 2020, also known as Misty, was a semi-experimental project between stable Zap and experimental Osada. On New Year's Eve 2022, it was officially discontinued and superseded by its own most recent descendent, the code of which resides in the Streams repository, and which is very similar in features and handling.
Mistpark 2020 no longer has active instances. It is no longer maintained; (streams) should be installed instead of it.