Thanks Stan, I found it today, under https://github.com/0ad-matters/gh-action-build-pyromod, and I will probably give it a shot! Looks like many devs come up with similar solutions to the same problems!
@andy5995 already wrote something for it https://github.com/0ADMods/ponies-ascendant/blob/master/.github/workflows/ponies-ascendant.yml
The advantage is that it is lighter to load cause it's using a custom mod of mine with what you need from public