For your information, YafaRay was successfully tested with Sweet Home 3D as a second rendering engine. See https://www.sweethome3d.com/blog/2018/0 ... _test.html and https://www.sweethome3d.com/blog/2020/0 ... ug_in.html
Even if it still doesn’t use GPU, I don’t have any intention to invest again a lot of time to try another rendering engine. If you have the capabilities to program a plug-in able to use another rendering engine, feel free to contribute inspiring yourself from YafaRay plug-in implementation.