I use the RaspBee Zigbee shield for RaspberryPi from Dresden Elektronik (35€ @amazon.de). It supports hue, lightify, innr, some chinese no-name products and Tradfri (even without firmware update to older bulps).
It also supports the tradfri motion sensors and remote controls (not the remote dimmer, sorry).
One big difference between the original Tradfri-Gateway and RaspBee: Using Tradfri-Gateway you can pair only one remote control to a bulb. With RaspBee every remote control is a “group” and you can add the bulps to more than one group. So if you need 3 remotes (instead of the wallswitches in a corridor) you can do it (with Tradfri-Gateway its impossible). The groups work even if you shut down the RaspBee (best WAF ever).
Instaling the software is somehow tricky, as graphical envirement is needed for the core component “deConz”. But you can do so remote; I installed it headles, starting deConz via autostart script.
For Tradfri you need an actual beta version of tje software (compile yourself…)
The RaspBee comes with an REST-API simulating an hue bridge with older firmware. It has some restrictions, not every app recognise it (and not all functions). For example the android app “all4hue” recognise bulbs and groups, but not scenes. Alexa recognise bulbs only (you can switch on, off and dimm, but not change colour or colourtemperature via voice). Of course using the web interface you can do all (control bulbs, groups and scenes).
I don’t use openhab now, but I don’t think it should be a problem. Even if it openhab would only recognise bulps, you could define the groups and scenes in openhab itself.
The only problem may occure if you want openhab to simulate an hue bridge itself - two hue bridge emulations on the same IP may not work. So maybe you need two RaspberryPi, one for openhub, one for RaspBee.
Of course a Raspberry Pi with RaspBee is a gateway…