Microsoft has officially moved all perpetual versions (like Office 2019 and 2021) to the C2R engine to reduce deployment costs and improve security. Benefits of Using C2R Office 365

: You can install C2R and MSI side-by-side only if the MSI product is from a different suite (e.g., Office 365 C2R + MSI Visio 2016). However, Microsoft recommends converting all MSI products to C2R.

The ODT is a command-line utility ( setup.exe ) coupled with an XML configuration file. It gives administrators granular control over the C2R installation.