It is due to Unity removing the built-in support for importing Substance materials. We were waiting for both Unity 2018.1 and the new Substance Unity plugin to be officially released (or at least the APIs finalized) before figuring out how best to support it via our plugin. For now, I have disabled Substance support for Unity 2018.x to get it working without the errors. This will be available in
tomorrow's build.
Though I do highly recommend using the new plugin version (v2) instead. This should be working in Unity 2018.x without errors, though with the same Substance import disabled.
https://www.sidefx.com/forum/topic/54483/ [
www.sidefx.com]