To initialize this project, use:
git clone --recurse-submodules https://github.com/AndreasNasman/frontend-masters.git
or
git clone https://github.com/AndreasNasman/frontend-masters.git
cd frontend-masters
git submodule update --init --recursive --remote
You can also use the latter command to apply upstream changes.
Then, to checkout a branch in each submodule (and exit detached HEAD state), run
git submodule foreach 'git switch solutions || git switch main || git switch master || git switch gh-pages && git pull'