I'm not sure if such a card exists. There are WiFi cards with free OS drivers (e.g. ath9k), but I would expect them to run some sort of firmware, too
according to wikipedia this ath9k family of WiFi controllers have both drivers and firmware as opensource. About USB controller, I didn't add xhci firmware image to my g505s coreboot and all the usb ports are working fine although at usb2 mode - so it seems to me that at least some controllers could function without a firmware, just that functionality could be degraded without one
Just to be sure, is the following a good way for flashing coreboot?
Maybe yes, although personally I'd have started with the largest amount of blobs and if it works then I did everything correctly and could try decreasing their quantity. This way you'd now if you're going the correct way right from the beginning, meanwhile your way is maybe more ethical but less confidence
Could you please explain that to me in more detail?
although I've never flashed t530 to me it seems pretty obvious: usually you connect your 8 wires to SPI flash chip and doing the flashing, but this time you'll connect 7 wires like usual to your programmer, but 8th CS wire to programmers VCC instead of programmers CS, and that programmers CS will be connected to CS of another chip