If you wish
The challenge is accepted!
I didn't need to run the Catalina installer on a surrogate Mac and then transplant the cloned partition over to the MBA as it ran without any quibbling directly on the target machine. Strangely, it wouldn't perform an upgrade of the Mojave partition and instead gave me the option of upgrading the El Capitan one instead. After a few minutes it rebooted to the iconic macOS grey install screen.
"23 minutes" transformed into several hours and the installer hung once the progress bar reached maximum. Eventually I initiated a hard reboot and the computer restarted.
It appears to have installed, but will it actually work? Let's log in and find out.
Ok, its successfully taken me through the configuration pages but what about the desktop itself?
Mission accomplished: contrary to Apple's claims and my own expectations, Catalina not only works on a 2GB machine - it appears to work
damn well too, considering the lean hardware its running on!
Once again Apple's shady behaviour is laid bare because this machine is up to the task of running an OS that they've officially barred from its upgrade path on what are clearly dishonest grounds: as with Tiger on my iMac G3/350 and my 2006 Mac Pro beyond Lion.
I'd have to replace many of my programs that are 32 bit in order to carry out a proper shakedown but so far I haven't seen the machine struggling and the fan hasn't activated during heavy activity such as watching HD content.
New Finder windows open quickly, the dock is fast and responsive and what programs I can open at the moment, spring into action fairly swiftly, all things considered. The question for me is whether I'll keep Catalina as a permanent addition. With only 256GB of drive space on my SSD, I'll have to reflect on the OS choices: Snow Leopard's presence is non-negotiable, Mojave works just as well as El Capitan and High Sierra - plus as we've already noted in this thread, it's the last macOS release with 32 bit compatibility so I could dispense with El Capitan and let Catalina use the partition space instead. What say you, my fellow MR members?
If you have any queries about Catalina running on my MBA or would like me to test anything out, go ahead and ask.