Hello jmuller ,
You can set speckle filter like this:
config = stereoDepthNode.initialConfig.get()
config.postProcessing.speckleFilter.enable = False
config.postProcessing.speckleFilter.speckleRange = 50
depth.stereoDepthNode.set(config)
This was taken from an example here. You can also see this example, which lets you change all postprocessing params in realtime to view the difference in depth output.
Thanks, Erik