Launching is only one result
A phone application can be designed around touch targets, swipes and an on-screen keyboard. A television player must be comfortable with the controls available from the sofa. If an application launches on an Android TV device, that result alone says nothing about whether every important action can be reached with its remote.
Start with the developer’s real television listing. VideoLAN, for example, identifies Android TV in its own Android distribution information. Use the actual publisher and supported platform rather than assuming an unrelated phone APK will provide the same interface.
Do not turn a control problem into an account problem
Suppose a selection cannot be reached with the directional pad. Changing a source URL or password will not establish the missing navigation route. Record the player name, version and the particular control that is inaccessible. A remote problem and a rejected login need different evidence.
If the developer does not offer the required television build, use a supported application or device route. A workaround that needs an extra mouse should be an explicit usability choice, not hidden inside a promise of universal Smart TV compatibility.
Questions answered
Does an app opening prove good television support?
No. Check the actual developer listing and whether the remote can complete the tasks you need.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.

