A significant challenge for the further scaling-up of quantum computing (QC) technologies based on platforms that use cryogenic technologies (e.g., ions, solid-state circuits, photonics, cold atoms) is how to efficiently multiplex large numbers of devices. Scaling up quantum computers to tackle real-world problems requires control interfaces capable of manipulating and reading out considerable numbers of qubits operating down to millikelvin temperatures. The focus is therefore shifting from the physics of individual qubits controlled with general-purpose room temperature instrumentation to scale-up engineering via dedicated and integrated cryo-systems.