The unstated is that the core problem here (lack of USB2 on a USB3 connector) is _NOT_ standard. This is generally only a problem on the plethera of shit arm/etc SoCs using garbage IP where the vendor is only interested in checking a box, than actually providing a working/compliant implementation of the specification.
Part two of this problem are the USB2 implementations that don't provide USB1 Transaction Translators (TT), so keyboards/etc won't work.
And as a 3rd note, the Pi4 actually has good USB3 because its implemented by a 3rd party XHCI controller like one might find on a random PCIe card. Combined with a usb3 hub with multiple TT's it should be possible to attach a number of SDR's etc at reasonable rates. Good luck figuring this out from the usb3 hub details unless it lists the chip its using.
Part two of this problem are the USB2 implementations that don't provide USB1 Transaction Translators (TT), so keyboards/etc won't work.
And as a 3rd note, the Pi4 actually has good USB3 because its implemented by a 3rd party XHCI controller like one might find on a random PCIe card. Combined with a usb3 hub with multiple TT's it should be possible to attach a number of SDR's etc at reasonable rates. Good luck figuring this out from the usb3 hub details unless it lists the chip its using.