Corona's ability to build for Linux (from Windows or macOS simulator) is further along than being able to run the simulator on Linux, but it's still Alpha at best and we are not working on it.
Linux, while may be a popular platform for developers, the reality is there is almost no way to monetize it as a developer. There are no app stores, beyond Steam and I'm not sure how popular Linux games and apps are on Steam. Steam has some micro-transaction features, but again I'm not sure how profitable they are. There are few if any ad SDK's for Linux.
Linux is a very open source oriented environment. People expect open source software which means no income potential for you as a developer.
I disagree with you in that one cannot make money with Linux. As you said, many of us use Linux as cross-platform development platform, but some of us also make money writing software for Linux. Agree that Linux games are not as popular as Windows ones and they seem no to sell well, but I write other software for macOS, Windows, Linux, AIX, Solaris and many other Unix incarnations and the ability of Linux to run on different hardware architectures allows me to do a lot of cross compiling using Linux.
Additionally I use Corona to build business apps that run on Windows, macOS, iOS and Android, as well as to teach kids game programming, which among many other things, allows them to understand physics concepts. Therefore, having the ability to run the simulator in Linux would save me money in licenses for teaching, and having the ability to build apps for Linux would allow me to produce my business apps for Linux as well as the other platforms, and believe me, there more and more businesses that run a lot of stuff on Linux.
So I think that at the moment, what we need is the ability to run the simulator in Linux, as wells as to be able to build FOR Linux, even if not FROM Linux. It would be nice to have that possibility in the future, but at the moment we could make the final builds on Windows or a mac, especially as one if needed to build for iPhones and iPads and those who do already own one.
I am extremely experienced writing cross-platform software in many languages, including C, C++ and assembler of few hardware platforms. And although I do not have a lot of free time, I would be interested on having access to the sources of the Linux efforts so I can build and run them on my systems, so I would be able to tweak and fix errors that I find, and contribute them to the community.