While headsets dedicated to mixed reality are increasingly considered to virtualize workspaces in the office, the keyboard remains mostly unchanged and nevertheless is still envisioned as an interface for common professional activities heavily demanding in text entry. However, unlike headsets, a keyboard is intrinsically limited to immobile context during its use, due to the need for physical support. In this article, we investigate a radical change in the structural shape of the keyboard, switching from the plane to a cube, allowing users to fully benefit from their whole environment by entering text in a much wider variety of contexts. We designed a cubic layout based on the QWERTY and results from two user studies to define the best holding position as well as fingers preferences and reachability to the cubic shape. Then, we conducted two subsequent user studies and one longitudinal case study to compare and evaluate typing skill transfer from the keyboard, learning curve, fingers usage, usability, and workload in various contexts. The cubic-shaped text entry device finally showed its versatility with users having similar performances while standing with a mixed-reality headset or sitting in front of a laptop, and an input speed from an expert reaching 55.1 wpm.