I cannot repro the null pointer reference with the latest LTS. However, the error message says "RenderTexture.Create failed: colorFormat & depthStencilFormat cannot both be none."
Setting a random depthStencilFormat fixes the issue. So right after,
RT = new RenderTexture(width, height, 0, RenderTextureFormat.ARGB32);
add one line,
RT.depthStencilFormat = GraphicsFormat.A10R10G10B10_XRSRGBPack32;
This fixes the issue.