Hello! Most of the Workshop avatars are 2D, so for those to appear in and work with FaceRig you will need the Live2D Module DLC: https://steamhost.cn/app/420680/FaceRig_Live2D_Module/

However, I want to underline the fact that FaceRig will be removed from Steam at the end of this month (this will not affect users that already have FaceRig and its DLCs in their Library). Furthermore, Animaze - our new software - has Live2D integrated by default and you don't need a DLC to use 2D avatars - either custom or from the Workshop. Animaze is also free to download and use.