Charge and USB keyboard through 1 USB port I have a Samsung Tab E that only has one USB port.

Can I charge the tablet and have a USB keyboard attached at the same time?

I've tried a 3-way cable ( link to Amazon ) but it supplies power to the keyboard, not the tablet.

I've also tried using a USB hub I had lying around, but I couldn't get that to work either.
The most likely way to use a keyboard while charging on a single port device is to use a Bluetooth keyboard.

Failing that, you may need a different 3-way cable.  The keyboard certainly needs power to operate (unless it has internal battery power), but a correctly wired 3-way cable should be able to both power the keyboard and charge the device.  You can verify that there's voltage on the charge pins of the two USB connectors on the 3-way cable, with a meter and suitable fine probes -- though it's very possible that the device will refuse to accept charge if there's a data attachment on the USB port.  You'd have to contact Samsung to verify that.