No heatmap shown with `seaborn` and `%matplotlib widget`

Start by reproducing the supplied seaborn heatmap and plain matplotlib plot in JupyterLab with %matplotlib widget, then compare them with %matplotlib inline. Inspect the ipympl and Jupyter widget integration used by this setup and verify the listed package versions. Done means the seaborn heatmap renders interactively with the widget backend.

Describe the issue

Thank you very much for providing this tool!

I have an apparently seaborn-related problem with showing widgets; I am posting this here first. Please let me know if you think this problem is rather on seaborn's end and I'll repost it there.

The problem: seaborn figures are not shown in JupyterLab with %matplotlib widget (they do show up with %matplotlib inline):

%matplotlib widget
import matplotlib.pyplot as plt
import pandas as pd
import seaborn as sns

df = pd.DataFrame([[10, 20, 30, 40], [50, 30, 8, 15],
                   [25, 14, 41, 8], [7, 14, 21, 28]])
sns.heatmap(df, cmap='RdYlGn', linewidths=0.30, annot=True)

%matplotlib inline
import matplotlib.pyplot as plt
import pandas as pd
import seaborn as sns

df = pd.DataFrame([[10, 20, 30, 40], [50, 30, 8, 15],
                   [25, 14, 41, 8], [7, 14, 21, 28]])
sns.heatmap(df, cmap='RdYlGn', linewidths=0.30, annot=True)

No problem with matplotlib:

%matplotlib widget
import matplotlib.pyplot as plt

plt.plot([[1, 2], [0, 0]])

Versions

ipympl version: 0.8.2
Selected Jupyter core packages...
IPython          : 7.29.0
ipykernel        : 6.4.2
ipywidgets       : 7.6.5
jupyter_client   : 7.0.6
jupyter_core     : 4.9.1
jupyter_server   : 1.11.2
jupyterlab       : 3.2.2
nbclient         : 0.5.5
nbconvert        : 6.2.0
nbformat         : 5.1.3
notebook         : 6.4.5
qtconsole        : not installed
traitlets        : 5.1.1
Known nbextensions:
  config dir: /home/dominique/.jupyter/nbconfig
    notebook section
      nbextensions_configurator/config_menu/main  enabled 
      - Validating: problems found:
        - require?  X nbextensions_configurator/config_menu/main
      contrib_nbextensions_help_item/main  enabled 
      - Validating: OK
      spellchecker/main  enabled 
      - Validating: OK
      gist_it/main  enabled 
      - Validating: OK
    tree section
      nbextensions_configurator/tree_tab/main  enabled 
      - Validating: problems found:
        - require?  X nbextensions_configurator/tree_tab/main
  config dir: /home/dominique/.local/miniconda/envs/test/etc/jupyter/nbconfig
    notebook section
      jupyter-matplotlib/extension  enabled 
      - Validating: OK
      jupyter-js-widgets/extension  enabled 
      - Validating: OK
JupyterLab v3.2.2
/home/dominique/.local/miniconda/envs/test/share/jupyter/labextensions
        jupyter-matplotlib v0.10.2 enabled OK
        @jupyter-widgets/jupyterlab-manager v3.0.1 enabled OK (python, jupyterlab_widgets)

Installed from conda-forge

mamba create -n test matplotlib pandas seaborn jupyterlab ipympl -y -c conda-forge

More versions:

# Name                    Version                   Build  Channel
matplotlib                3.4.3            py39hf3d152e_1    conda-forge
matplotlib-base           3.4.3            py39h2fa2bec_1    conda-forge
matplotlib-inline         0.1.3              pyhd8ed1ab_0    conda-forge
pandas                    1.3.4            py39hde0f152_1    conda-forge
seaborn                   0.11.2               hd8ed1ab_0    conda-forge
seaborn-base              0.11.2             pyhd8ed1ab_0    conda-forge

Do you have an idea why this is happening?