All of a sudden my USB ports became sluggish - 2020 Intel iMac

Hello

Not sure when, maybe it was around Ventura update, but I cannot be sure, I started to get really sluggish USB transfer speeds.

I have 2x USB 3.1 external SSDs hooked up to the same USB-C port through an USB 3.1 hub - one time I get advertised speeds, another time copying a 100MB file takes an hour.

But this is even more frustrating:

Today I tried to copy two files to an USB flash disk - total of 200MB - 4 hours.

I formatted the flash disk to FAT and exFAT (I need it to be visible in Windows) - to no avail.

I reset NVRAM, SMC. No change.

I disconnected those two SSDs and all my USB devices, and tried to repeat the copy process to my USB flash disk - same sluggish speed.

Of course I tried a bunch of different USB pendrives - same result.

Basically my USB ports are useless as far as using any flash disks.

I really can't remember what triggered it and when.

Any ideas are welcome.

Thanks!