My Computer is i7 -- yet it would not install with error code 21

Make sure your computer meets the minimum CPU & GPU requirements. Most Creative Cloud apps work on:

• Windows 10 versions 21H2, 21H1, 20H2, 2004, and 1909 (LTSB branches are not supported;)
• macOS 12 (Monterey), macOS 11 (Big Sur), macOS 10.16 or 10.15 (Catalina).

https://helpx.adobe.com/creative-cloud/system-requirements.html
https://helpx.adobe.com/dreamweaver/system-requirements.html

Error code 21: Payloads version is not supported by installed version of RIBS.

Reinstall the latest version of Creative Cloud Desktop App.  Restart your computer.