Thanks for the responses.
@justclaws:
2. Yes, Ubuntu 20.04 LTS would be compatible, but remove all unnecessary services, like the VCS.
I am new to Linux. Any pointers on how to pare it down to the essentials?
3. It is possible to overwrite the VCS system software, as it's just an eMMC, but not a good idea
I should have been more clear: I guess what I am looking for is a way to install another OS side by side with the Atari OS, so I can easily choose between the two for development. Based on what I have now read, that doesn't seem to be the case. I'd settle for an external drive with a switch on it: flip it on to autoboot into ubuntu, flip it off to boot into Atari OS.
4. The only Unreal developer I know of, is a hobby developer, who was working on "PitFOOL VCS", but he got the Classic joystick spinner working in his demo.
I did come across those posts since I originally created the thread. I believe he wasn't deploying to the hardware, and instead running off of his Mac/PC. I imagine he got the Atari stick working using the RawInput plugin in Unreal. Cool, though! At least I am not totally alone here.
Not much more work from me on VCS dev at this point. Looking forward to tinkering on the weekend.