The Candeo dimmer is already on the list but there are lots more. It isnt always easy to find devices in the UK and this list often the first place people visit when beginning their device purchase journey - it will help keep boxes/draws of doom devices smaller.
Also - is it possible in future to have a region/country filter? This will help narrow down ones that are likely to be available in a particular location and also more likely to comply with standards and codes?
Officially supported devices are those that have drivers written by and tested by the Hubitat developers. Some devices are able to use common drivers they have written, but many require drivers written specifically for the device. You can get in touch with the dev's here on the Community and discuss options for getting a driver created / tested. For many devices it may involve getting one sent to them so they can test it adequately, which may involve sending one you have purchased or that the manufacturer is prepared to offer for free.
I agree this would be useful, but my suspicion is that this would likely be time consuming to keep tabs on in terms of device availability in different regions. If someone is prepared to regularly scour the various sales websites across the globe per device and keep a Wiki up-to-date, that would be great.