checkout@v3 unable to update submodule with "git://" url

[achsvg]

We have a submodule configured with "git://" url in .gitmodules

[submodule "submod"]
	path = submod
	url = git://github.com/.../submod.git

When making a change in submod and pushing the ref update to the parent repo, checkout is unable to pickup the new commit:

Fetching submodules
  /usr/bin/git submodule sync --recursive
  Synchronizing submodule url for 'submod'
  /usr/bin/git -c protocol.version=2 submodule update --init --force --depth=1 --recursive
  Error: fatal: unable to connect to github.com:
  github.com[0: 192.x.x.x]: errno=Connection timed out
  
  Unable to fetch in submodule path 'ml-models'; trying to directly fetch <hash of the commit>:
  Error: fatal: unable to connect to github.com:
  github.com[0: 192.x.x.x]: errno=Connection timed out
  
  Fetched in submodule path 'submod', but it did not contain <hash of the commit>. Direct fetching of that commit failed.
  ##[debug]Unsetting HOME override
  ::remove-matcher owner=checkout-git::
  ##[debug]Removed matchers: 'checkout-git'
  Error: The process '/usr/bin/git' failed with exit code 1
  ##[debug]Node Action run completed with exit code 1
  ##[debug]Save intra-action state isPost = true
  ##[debug]Save intra-action state setSafeDirectory = true
  ##[debug]Save intra-action state repositoryPath = /home/ubuntu/actions-runner/_work/xxx/xxx
  ##[debug]Finishing: Run actions/checkout@v3

Changing the scheme to https works.