dcc.Graph with Scattergl renders empty after update to Plotly 6

[fgiaret]

The sample code below plots a Figure with some Scattergl traces, rendered inside a dcc.Graph component.
Each trace has mode “lines+text”.
With Plotly 5 this used to work as expected; after updating to Plotly >= 6.0.0, the graph component still loads, but no data points are visible.
No errors are shown in the browser console or Python logs (as a note, Dash 3 was used).

Sample Code

import dash
from dash import dcc, html
import plotly.graph_objs as go
import numpy as np

# Generate data for many scattergl traces
num_points = 10000
num_traces = 4

traces = []
for i in range(num_traces):
    x = np.arange(num_points)
    y = np.random.rand(num_points) + i
    customdata = [f"Trace {i+1} - Point {j}" for j in range(num_points)]
    labels = [f"Trace {i+1} - Point {j}" if j==0 else "" for j in range(num_points)]
    
    trace = go.Scattergl(
        x=x, 
        y=y, 
        mode='lines+text', 
        name=f'Trace {i+1}',
        customdata=customdata,
        text=labels,
        textposition='top center',
        hovertemplate="%{customdata}<br>X: %{x}<br>Y: %{y}<extra></extra>"
    )
    
    traces.append(trace)

# Create the figure
fig = go.Figure(data=traces)
fig.update_layout(title=f'ScatterGL with {num_traces} Traces', xaxis_title='X', yaxis_title='Y')

# Create Dash app
app = dash.Dash(__name__)
app.layout = html.Div([
    html.H1("Dash ScatterGL Example"),
    dcc.Graph(figure=fig)
])

if __name__ == "__main__":
    app.run(debug=True)

Turning Scattergl mode from “lines+text” into “lines” restores the expected behaviour.
Playing with the number of traces or data points seems to have no effect.

Environment
The issue occurs with the following environment:

Python version: 3.9.7
Dash version: 3.2.0
Plotly version: 6.3.0
Browser: Chrome 139
OS: Windows 11
As already mentioned, downgrading Plotly (e.g. from version 6.3.0 to 5.24.1) restores the expected behaviour.