List current HEAD commit in each submodule

git submodule foreach 'git rev-parse HEAD'

List current checked-out branch in each submodule

git submodule foreach 'git rev-parse --abbrev-ref HEAD'

Batch remote management in submodules

git submodule foreach 'git remote -v'
git submodule foreach 'git remote set-url example ssh://git@gitea.example.org/EXAMPLE/$name.git'
git submodule foreach 'git remote add example $(git remote get-url origin | sed "s/XXXX/YYYY/") || true'

Other

git submodule foreach 'git fetch --all'
git submodule foreach 'git branch -u zertrin/marc zertrin-gitea'

Link to old tutorial in french fr-tuto