How can I connect a hue bulb directly with the smartthings hub without a hue bridge
use the scan option when adding a device. While this option works, it isn’t recommended since SmartThings has no way of resetting Hue devices. You have to use a hue bridge, hue dimmer switch or Alexa device with Zigbee to reset Hue lights.
Also hue bulbs turn out to be particularly poor Zigbee repeaters when paired directly to a ST hub and can mess up your SmartThings Zigbee network if used without a Hue bridge.
Definitely would recommend a Hue Hub. Connectivity is so much better, and you get many more options for integration.