I cannot seem to find the "all in one" download link for all of the submission entries. It would be really great if this were available.

We were just talking about adding a pre-packaged zip for this, but haven't done it yet.

In the mean time you can go to the github repo at the following URL, click the "Code" button toward the Right side and then click "Download ZIP". You'll get some extra stuff in there, but it will have all the entries and you can search for ".gb" and ".gbc".

https://github.com/gbdev/gbcompo21

Thank you very much. This was very helpful.