Using python v3.6.9 & plotly v4.14.1 on Chrome I get several different bugs with Heatmapgl:

1. When adding Heatmapgl to a subplot, nothing's shown.
2. Heatmapgl has "fast" zsmoothing by default (in contrast to Heatmap which is False).
3. Heatmapgl's zsmooth=False results in a truncated auto-view.
4. Heatmapgl's does not allow zooming/panning from the axes, and double-click doesn't work.
5. Heatmapgl's toolbar has a lot less options.

This trace feels half-baked. It is really too-bad that I can not use it because I wished to show large spectrograms, and I can't using plotly.

In more detail:

Consider the following code:

import plotly.graph_objs as go
from plotly.subplots import make_subplots

fig = make_subplots(rows=1, cols=2)
fig.add_trace(go.Heatmapgl(z=[[0, 1, 2], [2, 0, 1], [1, 2, 0]], colorscale='Picnic'), row=1, col=1)
fig.add_trace(go.Heatmap(z=[[0, 1, 2], [2, 0, 1], [1, 2, 0]], colorscale='Picnic'), row=1, col=2)
fig.show(renderrer='browser')

And I get a blamk page with a color bar:

Note that the same happens with other kinds of traces as secondary to Heatmapgl (like Scattergl).

Now, if I comment-out either lines, I get the traces as expected, only that for the Heatmapgl, I get a strange smoothing by default:

So I went ahead and set zsmooth=False for the Heatmapgl, and I got:

Note the missing buttons in the toolbar ("spike-lines" and "compare" which exist in Heatmap). I wasn't able to pan and zoom the plot by dragging the axes in the usual places. Also, after panning using the toolbar button, double-click did not return me to the original view.

Thanks.