Side note: if we want to add VM ova files to Zenodo in future, as mentioned before I'd recommend adding the files to CCPPETMR/SIRF github releases via the web interface.

Does this mean we have to upload to GitHub?

Yes - as part of the release checklist during the "create a github release" stage - you'd have to first create ova file(s) so that you can upload them when creating the release. As I'd mentioned before, there is no limit to number of files uploaded, but individual files must be <2GB (hence discussions on splitting the VM into multiple images)