There is discussion on both the Apple board and SoftRAID blog. Someone didn’t do their QA and 15.2 hangs on installation, recovery, and boot if any Thunderbolt peripherals are connected.
The workaround is the same for all 3 situations: Unplug everything except your mouse, keyboard, and monitor, then plug them in when the installer or OS is ready for user interaction.
I think the title should be “Mac Pro 2019 + macOS 15.2 + TB peripherals = no-go”. My MacPro 2019 running 15.2 has only the monitor connected by TB It works reasonably well, although it still has a number of macOS bugs. Making this distinction is significant because
"Mac Pro 2019 + any macOS < 15.2 = no-go”
This is because macOS has long had many bugs, especially in Intel code, and in parts needed for devices via the MacPro’s PCIe slots. Extensive work by Apple and OWC got rid of many of these bugs, but not all, in macOS 15. The cleanup of macOS has continued with subsequent point releases, but some remain in 15.2.
So actually, macOS 15.2 may be the best you can get for a MacPro 2019. Even if you have to disconnect your TB peripherals on reboot.
You are correct. I’ll see if I can go back and make an edit.
Ron