the SHA hashes were updated to SHA256 in version 18.05: (...) Apparently, we missed to update the Atari800 port.
In contrast to the content of the 'genode' repository, the content of the 'genode-world' repository is not subject to automated tests. So the issue remained undetected. Thank you for reporting it! Would you like to submit a patch with a fix? ;-)
That explains it. Thanks for your response. I've created a pull request for this fix: https://github.com/genodelabs/genode-world/pull/121
Regards, Wouter