How necessary is it to activate in windows? I don't have windows on my machine.
To be totally frank, I am not all that sure. I don't have any TB3 devices (currently, but some are on the way), and have been using it for small USB-C devices (Card readers, external drive dock, etc.). There's reports of the card working just with SSDT patches and that's it, but also reports of the card not initializing at all until activated in Windows. Mine initialized immediately, but again, without hands-on device testing, I can't say for certain.