The latest generations of gnss receivers have spoofing and jamming mitigation and detection features included with the chip, and multi-band rx technology to sync to more constellations simultaneously and do exactly what you’re talking about. Before then, the spoofing/jamming detection would likely need a software implementation after the receiver. There are different types of spoofing/jamming, all of which are detected and mitigated in different ways.

I don’t know the commercial aircraft industry standards for updating technology, but I wouldn’t be surprised if most commercial aircraft don’t have what you’re talking about.

It means for the first 20 years they spent all of their profit on expansion / R&D

I just looked at the GitHub repo for that project. Are there any tutorials or anything out there for it that make the setup easy?

Did you also get paid for the time you spent traveling?

Yes, you can code in machine code. I did it as part of my CS Degree. In our textbook was the manual for the particular ARM processor we coded for, that had every processor-specific command. We did that for a few of the early projects in the course, then moved onto Assembly, then C.