Arnold converter is an initiative based around the Scene converter tool.
Primary focus is to tackle Vray and Corona materials, shaders and lights and other legacy constucts.
The project is a couple of months old so far but I do have a stack of closure and shader support up and running already. You can check the supported list on the site beneath.
You can head over here -> https://www.masd.dk/arnoldconverter/ and get a copy and try it out.
I also added a couple of custom OSL shaders that I wrote to cover for Vray Color and Corona Color for example.
I have more custom OSL nodes on the table that are targeted to replace Vray and Corona maps.
If you use it and find some things that does not work as expected or you have some things, reach out and get in contact and Ill look at it.
In general I go for writing custom OSL shaders or use shipping OSL shaders to untangle Vray and Corona from propitary shaders but may resolve to c++ Arnold nodes in certain cases.