AppDaemon apps are apps for AppDaemon
Since not all users are running AppDaemon, AppDaemon is not enabled by default in HACS.
Enable AppDaemon apps in HACS
There are 2 ways of doing this.
Enable if you used the UI to configure HACS
Add a checkmark to the left of AppDaemon apps in the UI configuration for HACS.
For more about configure HACS with the UI have a look here
Enable if you used the YAML to configure HACS
If you used YAML to configure HACS, add this under your HACS connfiguration to enable AppDaemon apps.
hacs:...appdaemon: true
When you have done that you need to restart Home Assistant.
For more about configure HACS with YAML have a look here
AppDaemon apps download location
All the AppDaemon apps you download with HACS is stored in appdaemon/apps/ in your Home Assistant configuration directory.