If you build a non-humanoid avatar with no "avatar" asset set on its animator, and attach a custom expressions menu, your custom expressions menu is ignored in-game, and instead you see just the Quick Actions menu.

Repro unitypackage: https://www.dropbox.com/scl/fi/7kihjwiijm5c35m4obwei/no-exp-menu-repro.unitypackage?rlkey=j0ehysemsu9j9trsaq07nsrzx&st=96dfderc&dl=0

Tested with VRCSDK 3.9.1-beta.2.