[ksec]

>Thunderbolt is now officially dead

There is, actually Thunderbolt 4. It is in no way dead. To what extend this is different to TB3 is unclear yet.

>it has been absorbed into the official USB4 standard.

Not Strictly true. TB is not a mandatory part of USB 4 standard. Which means you will likely have lots of USB 4 controller without TB support. ( Cause It will be cheaper )

>There is very unclear support for existing Thunderbolt-over-Type-C devices under USB4

It will work as long as your USB4 has support and certified with TB. You will have to use a TB cable ( which you should have if you are already using it ) instead of any USB-C cable.

How exactly will TB certification works without involving Intel is still unclear.