I'm afraid I cannot be of much help with this. I can only speak about the Windows builds and all I can say is that I have serious doubts that a successful nightly can be generated. The dev environment used on Windows is a very specifically set up version of an older MinGW, aimed at giving you an executable Oolite installer at the end of the build process with just one command, when starting from a clean master branch checkout. Trying to build in any other environment, like a standard MinGW install without the exact necessary libraries for linking is not guaranteed to work as intended. To add to that, MSVC (accesible in various versions from within github actions) is right out of the question for building Oolite. You are more than welcome to try if you want, but I can already see blocking issues in the horizon. The reason it worked in the nightly generation system we had until recently is that a copy of the "correct" build environment was running on terrastorage, the nightly production server which was recently decommissioned, so a successful build was always guaranteed. If github could get access somehow to that specific build environment and its actions somehow be made to make use of it, then there could be a chance. Unfortunately, I haven't got the slightest idea how one would go about it.
Mac builds may also be another issue because the Xcode version targeted for generating them is an old one and I can see already the github actions in your PR are complaining about it. There is code somewhere in the Oolite repository for updating Xcode support to newer versions but we never used it because it would have broken compatibility with the Xcode we were using for making the Mac nightlies back then, which meant that the Mac nightlies would have stopped being generated much earlier than they finally did.
Linux, with its standard gcc support and not requiring a specific dev environment setup, might actually be the one that has the highest chance of working. It is also your OS of choice, so it should be theoretically easier to work with that anyway. And yes, DevOps is hard.