Yep that worked, so my workflow gh-pages includes this line:
jobs:
deploy:
runs-on: ubuntu-20.04
steps:
- uses: actions/checkout@v2
with:
submodules: true # Fetch Hugo themes (true OR recursive)
fetch-depth: 0 # Fetch all history for .GitInfo and .Lastmod
lfs: true # Fetches LFS data
...