What happened to all documentation that was on the web page for the python library? It's all gone and replaced by the pmxt API online service.

Will that same type of REST api be available for the python library and pmxt sidecar locally?

The mintlify docs show both the local and the hosted docs. If you don't pass your pmxt api key, you're using the local version. For each endpoint under the api reference, change language in the drop down to python.