Configuring SSH Keys for Multiple GitHub Accounts

Host github.com
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_fry_ed25519

Host github-plnx
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_fry_plnx_ed25519

# Instead of the actual URL
$ git clone git@github.com:planet-express/delivery_service.git

# Substitue in our custom Host value for the `github.com` part
$ git clone git@github-plnx:planet-express/delivery_service.git

[include]
  path = ~/.gitconfig_custom

# See custom `Host github-plnx` in ~/.ssh/config
[url "github-plnx:planet-express"]
  insteadOf = git@github.com:planet-express