I bought a USB 3 PCI-e card to add to my 2010 Mac Pro 5,1. Unfortunately, the drivers did not load soon enough in the boot process to allow me to boot from a drive connected to the card. I could still use it for external data drives.

Looking forward to seeing how computers have changed in nine years. I no longer do the work that requires an iMac Pro, so just went with the mid model.

I will be using the old Mac Pro as a server following the instructions I received here, thank you very much.

iMac (19,1, 3.1 GHz i5, 12.7.4, 40 Gb RAM); MacBook Air (1.8 Ghz, 8 Gb RAM, 10.14.6, 256 Gb SSD) Vodafone router and Devolo Wi-Fi Extender, Canon TS8351 printer/scanner.