Currently, Bamboo doesn't add SSH keys to the Github repository type or its submodules, like the Bitbucket server repository type.
SSH keys need to be generated on each and every agent that runs the checkout of that repository in Bamboo, and those SSH keys should be manually added to Github repositories/submodules for successful source code checkout.
This will become a tedious task to add SSH keys manually if we have a large number of Github type repos with submodules.

It would be helpful if Bamboo could add SSH keys for Github type repositories, like Bitbucket server type repositories.