Most Elgato software now supports macOS 10.15 Catalina,
This is true as of October 7, 2019 - the day macOS 10.15 was originally released.
As of October 8, 2019, the full lineup of applications now supports Catalina.
Supported Software Out Now:
Control Center (1.1 and above)
Game Capture HD (2.11.8 and above)
OBS Link (1.0 and above)
Stream Deck (4.3.3 and above)
Thunderbolt Dock Utility (1.2.10 and above)
Video Capture (2.0.1 and above)
If you haven't already, please visit the Elgato Downloads page to upgrade to the latest versions.