MP 1,1-5,1 Mac App Store nightmare, can't use or create an account

[Macmillennial]

Apple... apple...
I've installed a new nvme and really want to benchmark it.
I've tried to download software from the Mac App Store with my iPhone account but it say that I need macOS 13 and creating a new one give random errors, both from store and web site.
How do you guy have solved this?
Thanks

 

[Bigwaff]

What model Mac Pro? What version of macOS do you currently have installed?

 

[Macmillennial]

CMP 5,1. High sierra last version, last patch. Thanks!