Hi guys, I wanted to give a little update on my situation, it might help other that have the same issue.
Just like bj00rn, I bought a PCI-E expansion card that solved everything!
Unfortunatelly I had a micro ATX case, so I had to get a bigger one to fit the additionnal card, and as I also have a micro ATX motherboard and a big RTX3080, I had to buy a PCI-E X1 90° cable as the graphics card is hiding the additionnal PCI-E slots.
To sum it up:
- USB powered hub: tried, didn’t work
- PCI-E extension card: works like a charm!
The card I bought: SupaHub PCI-E USB 3.0 expansion card (4 ports).
(It has an internal SATA power supply that I didn’t have to connect, it seems that the PCI-E port gives enough juice.)