How to add static labels to plotly express `choropleth_mapbox`?

• the obvious answer is add a Scattermapbox layer with text that you want. This is complicated by this bug. I did not find an clear replacement for carto-positron as a replacement on https://www.mapbox.com so the map style has changed
• create an account on https://account.mapbox.com to get a token, create a base map on https://studio.mapbox.com to create a base map
• also tried using plotly annotations. However I could not find a way of getting bounding box of map to be able to transform lat/lot co-ords onto domain co-ords (0-1)

mapboxtoken="****"
mapboxstyle="mapbox://styles/***"

• use geopandas for simple access to centroid of geometries

import plotly.express as px
import plotly.graph_objects as go
import geopandas as gpd

df = px.data.election()
geojson = px.data.election_geojson()
gdf = (
    gpd.GeoDataFrame.from_features(geojson)
    .merge(df, on="district")
    .assign(lat=lambda d: d.geometry.centroid.y, lon=lambda d: d.geometry.centroid.x)
    .set_index("district", drop=False)
)

# for convenience of rebuilding and adding traces...
def basemap():
    fig = px.choropleth_mapbox(
        df,
        geojson=geojson,
        color="Bergeron",
        locations="district",
        featureidkey="properties.district",
        center={"lat": 45.5517, "lon": -73.7073},
        mapbox_style=mapboxstyle,
#         mapbox_style="carto-positron",
        zoom=9,
    )
    fig.update_layout(margin={"r": 0, "t": 0, "l": 0, "b": 0},
                      mapbox={"accesstoken":mapboxtoken}
                     )
    return fig

pull it all together

texttrace = go.Scattermapbox(
        lat=gdf.geometry.centroid.y,
        lon=gdf.geometry.centroid.x,
        text=gdf["Bergeron"].astype(str),
        textfont={"color":"white","size":20, "family":"Courier New"},
        mode="text",
        name="Bergeron"
    )

basemap().add_trace(texttrace)

output