Install ipywidgets in base
I consider it part of base notebook install :)
MODIFY
singleuser-builder/Dockerfile
singleuser-builder/Dockerfile
@@ -24,7 +24,7 @@ WORKDIR /home/jovyan
USER jovyan
RUN python3 -m venv ${APP_DIR}/venv
-RUN ${APP_DIR}/venv/bin/pip install --no-cache-dir notebook==5.0.0 jupyterhub==0.7.2
+RUN ${APP_DIR}/venv/bin/pip install --no-cache-dir notebook==5.0.0 jupyterhub==0.7.2 ipywidgets==5.2.3
COPY ./s2i/bin/ /usr/libexec/s2i

Install ipywidgets in base

I consider it part of base notebook install :)