Please do the following correction in your code then you will be able to get the ExplainerDashboard.

1) Set the Environment variables in Databricks Cluster

For example :

DASH_REQUEST_PATHNAME_PREFIX=/driver-proxy/o/4080082044610008/1004-091920-cxkidhkx/8888

Workspace ID : 4080082044610008 

Cluster-ID: 1004-091920-cxkidhkx 

Port number : 8888

2) Install the explainerdashboard library

%pip install explainerdashboard

3) Sample code for to validate the "dash" 

from sklearn.ensemble import RandomForestClassifier

from explainerdashboard import ClassifierExplainer, ExplainerDashboard

from explainerdashboard.datasets import titanic_survive, feature_descriptions

X_train, y_train, X_test, y_test = titanic_survive()

model = RandomForestClassifier(n_estimators=50, max_depth=10).fit(X_train, y_train)

explainer = ClassifierExplainer(model, X_test, y_test,

   cats=['Deck', 'Embarked'],

   descriptions=feature_descriptions,

   labels=['Not survived', 'Survived'])

ExplainerDashboard(explainer, mode = 'dash',

   importances=False,

   model_summary=False,

   contributions=True,

   whatif=False,

   shap_dependence=False,

   shap_interaction=False,

   decision_trees=False).run(8888)

4) Dashboard URL

https://xxxxxxxx.databricks.com/driver-proxy/o/4080082044610008/1004-091920-cxkidhkx/8888