Hey Dennis,
Sorry about this – we have recently updated the Pathfinder implementation, which no longer uses the Blackjax library by default. Once we cut a new release of pymc-examples (which will hopefully happen in the next few days), the notebook will be updated also. If you want to use the Blackjax implementation, adding an inference_backend="blackjax" argument to pmx.fit should work. The PyMC implementation does not yet use JAX, but has other nice features that the Blackjax version does not have, such as multi-path Pathfinder.