I had started this thread with the hope that among the many Perl experts here on Perlmonks there would be somebody using a M1/M2 Mac with MacPorts Perl who could run my test script and confirm or disprove the issue

That was reasonable but it's been a week now and nobody has. I suspect that is because the hardware is newish and expensive and only really of use/interest to appleheads. So, why not inquire of your CI provider whether they support it or not? A cursory search has shown that Circle CI and Cirrus CI do - or at least claim to.

I neither write code for nor actively support proprietary systems but like you I still try to help out such users where I can and in those situations CI is invaluable. YMMV, of course.

Alternatively, you could spin up a VM with your favourite cloud provider for a couple of minutes just to run the code and find out that way.