I've been able to debug PostgreSQL issues reported by [closed] Solaris users by booting illumos inside a virtual machine on my laptop in minutes...
I want to keep AIX support, for, well mainly irrational nostalgic reasons -- PostgreSQL used to run on pretty much the entire Unix family tree, and I wrote lots of code on AIX for a decade. But they make it hard. I don't know why an OS vendor wouldn't make an image of an OS available to developers as conveniently as possible (it is even possible to boot recent AIX versions on QEMU if you have the patience... the hypothesis is that they might have done work to make that possible, 'cause it didn't work in earlier versions; but you can't get an image of OS, so shrug).
The easiest legal way to get an AIX box is via IBM Cloud. You can get a tiny AIX box (s922 in Dallas, 0.25 cores, 2GB RAM, 10GB disk) for about US$50 a month. About US$8/month of that is AIX licensing and the rest is the hardware cost. Still a lot cheaper than IBM i licensing, which is US$350/month even for such a low-end system, or IBM Z (which is around US$1600/month for a low-end system).
IBM Cloud does offer some free credits – at the moment US$1000 free VPC credits – but I'm not sure if you can use them on AIX (which isn't part of their main VPC offering, POWER is a separate offering), and even if you can, they aren't going to last forever.
If one is an open source developer doing this on one's own time, as opposed to a business – why spend US$50/month to get an AIX environment? Maybe, if a user of the project really wants AIX support, they could donate that to the project.
I've been able to debug PostgreSQL issues reported by [closed] Solaris users by booting illumos inside a virtual machine on my laptop in minutes...
I want to keep AIX support, for, well mainly irrational nostalgic reasons -- PostgreSQL used to run on pretty much the entire Unix family tree, and I wrote lots of code on AIX for a decade. But they make it hard. I don't know why an OS vendor wouldn't make an image of an OS available to developers as conveniently as possible (it is even possible to boot recent AIX versions on QEMU if you have the patience... the hypothesis is that they might have done work to make that possible, 'cause it didn't work in earlier versions; but you can't get an image of OS, so shrug).