Ipyleaflet-ipywidgets package versioning with Popup on GitHub Pages

I’m trying to get Popup in ipywidgets to work with my ipyleaflet map on GitHub pages, but Popup doesn’t work unless I use an older version of ipywidgets (7.7.2).

My requirements.txt includes the ipywidgets version AND the version of ipyleaflet:

shiny
shinywidgets
pandas
geopandas
numpy
plotly
ipywidgets==7.7.2
ipyleaflet==0.19.0

my deploy.yml contains:
- name: Install dependencies
run: pip install -r source/requirements.txt

which should install the correct ipywidgets version. Also, it does work locally but not on GitHub.

Any suggestions as to how I can fix this? Would be happy to provide my repo as well if that is helpful.