Launched around the same time as Catalina, this version was designed for 10.15 compatibility. The 32-Bit Problem: Legacy Versions (CS6 and Older) Is Mac OS Catalina 10.15.1 compatible with Illustrator 24.0
This is the last major release officially compatible with macOS Catalina. adobe illustrator macos catalina
Because Adobe typically supports the current version and one previous version, finding a compatible download for an older OS like Catalina can be difficult. Launched around the same time as Catalina, this
Can't Install Illustrator on macOS Catalina - Adobe Community adobe illustrator macos catalina