thoreboj :
I'm really confused about how Thunderbolt 3 works on PC. Is every motherboard with a type c port Thunderbolt compatible? I'm looking for a decent Z390 motherboard that can handle Thunderbolt 3 (Preferably ATX)
Just because there is USB Type-C does not automatically asssumed that it supports Thunderbolt or even some of the other standards.
USB C (Type-C) is a connector shape and it could support Thunderbolt, HDMI, VGA, DisplayPort, power delivery and intake.
Also, you should use a cable that it is compatible with the standard you want to use.
GIGABYTE Z390 DESIGNARE supports Thunderbolt 3 thru the USB Type-C (3.1 Gen2)