With a kid in the house during the holidays fighting the volume of various devices has become one of my main struggles.
This has actually lead to all kinds of strange tools, but one of the most effective is also one of the simplest. A tiny little C# program which polls the volume of our FireTV and adjusts the volume if it exceeds a certain limit, by default 0.5.
If you’re a parent and comfortable using ADB, you can get the binary and source at https://github.com/hansschmucker/FireTV-VolumeLimiter/releases
I have to be brutally honest here… I’m at a total loss why no OS manufacturer includes this out of the box. We have iOS, macOS, Windows, Android, FireOS and not a single one allows setting the maximum volume level for restricted users.