The HUGIN QGIS BBN plugin is now available for QGIS3.
The QGIS Processing script makes it possible to apply a Bayesian network to each point in one or more raster layers and output a new raster layer with the results. For each point potentially covering multiple layers, the Bayesian network inserts and propagates the values of the nodes linked to raster layers. The user can select a number of output values: index of state with maximum probability, probability of state with maximum probability, and maximum expected utility.
More information here: http://plugins.qgis.org/plugins/hugin_qgis/