Anyway to make my object not fall through the floor without convex?

Your Rigidbody must be Convex MeshCollider or not mesh-based at all i.e.: SphereCollider, CapsuleCollider, BoxCollider.

This change was introduced because collisions between two non-convex meshes are known for being computationally expensive so were causing performance issues for all the newcomers not yet familiar with this subject.