Foveons don't actually de-bayer bc they use a stacked 3-layer sensor, where each layer is sensitive to different colors. The top layer is RGB, the middle is just RG, and the bottom is just R. We calculate the three values by subtracting the layers from each other.
Traditionally all processing of these X3F RAW files had to go thru software provided by Sigma, and its clunky and bakes in some processing you can't really turn off. Some folks (myself among them) are focused on creating new ways of processing and converting these X3F files to be used more flexibly. I have some links in the threads other replies to some changes I made to one processor.
I was able to significantly improve the highlight recovery. It's kind of a game changer since the sensor architecture requires a LOT of light to get the best results. To minimize noise you expose to the right at least one stop and then pull down in post. With the new processing I am able to get pleasing results closer to +1.7 and sometimes even 2ev. This sensor was not known for having great dynamic range, but with extra processing you can tease some information out into something attractive. It does leave the upper end of specular highlights flattened compared to a proper exposure but it often looks "believable" so I'm happy with it.