Comment # 1 on bug 1045891 from Heinz Kohl

In thoughts I connected a CF card over an USB2 multiplexer into a USB3 slot -
and surprisingly, that worked.
This was the first device which was unknown by KDE connect.

After that, USB3 devices are also working directly in a USB3 slot, but not a
USB2 stick. This not working device is a USB2 stick, which was formely holding
a OpenSuse 42.1 distro. After formatting it as  new, it's still bearing the
name of this distro (openSUSE-42.1-DVD-x86_640148) and it's to expect, that
there's still the OpenSuse boot sector. 
Up to now this was no problem.
I would have understood, when this is not working because of firewall action,
but no other device? (Beside of that, I think, the first USB3 stick I tried
with this kernel version, was another stick, and it failed. And that even after
a new boot).