When I type the command in adb:
./adb shell am start -W -a android.intent.action.VIEW -d \"example:gizmos\" com.myapp
I get this error:
As the other answer mentioned, it should be "example://gizmos" and not "example:gizmos"
Alternatively, instead of using adb, you can test deep links directly on android using deep link tester app:
https://play.google.com/store/apps/details?id=com.manoj.dlt
No need to mention any package name or component name. Just type the deep link and fire.
I've found testing deep links through adb to be cubersome and difficult at times. Hence, I've built this small app to do it.