At its heart, the 4.4.0 update (specifically the 4.4.0.1 bugfix release) is powered by the Arnold 7.1.3.2
Render complete. 1,280,000,000 rays cast. 0 lost. 1 ghost found.
Builds after 4.5.0 dropped support for R21–R23, so don’t install newer Arnold expecting compatibility.
, its core features, and its integration across Maxon's legacy versions like R21, R22, and R23.