Remarkable! This is the most relevant addressing of the problem. Even if it doesn't fully resolve some final doubts, I can attest that "Language" (🌐) can be one mechanism by which the mic function could be lost. (And one of my prior suspicions.)
This is how I set out to test. My Apple TV is set up with three languages (⚙️General→Apple TV Languages), two of them are found listed in ⚙️General→Siri Language. In an odd twist, the third "language" is not supported in Siri even though a very slightly different variant is.
Before testing, you also want to be familiar with two terms Apple uses: "Siri" and "Dictate". They behave very similarly, use the same voice recognition engine in the backend, but Apple TV differentiates them judiciously. In Settings(⚙️)→General, "Dictation" is enabled/disabled under "LANGUAGE & REGION" while "Siri" is enabled/disabled under "SIRI". "Dictation" setting applies inside an app, including third-party apps such as Youtube, 🍏TV app, even the built-in Search app, but only when you navigate to the app's "Search" (🔍) menu AND engages the on-screen keyboard. Anywhere else, including in Apple TV's home screen, Siri is in charge. The practical difference is that "Dictate" allows you to use voice to interact with an app's own search function, while "Siri" interacts with an invisible (Siri) app to perform a function, e.g., "OPEN crossy road;" if Siri cannot recognize the first word as a command, it executes a "SEARCH" command with your voice input. In the latter case, the search result will be the same as if you entered the search in "Search" app, but the results are displayed as a side bar on the current screen, not as a list in Search app.
With this, I tested "Dictation" function (which is also the foundation of Siri) by invoking the on-screen keyboard in an app. Every time I click the globe icon (🌐), Apple TV switches to a different language; most commonly it cycles through the three although depending on your prior use, sometimes Apple TV tries to "predict" what you want to switch to. Anyway, whenever I land in one of Siri-supported languages, the screen displays a prompt "Press 🎤to dictate in XXX." At this prompt, I can press the mic button on remote. Apple TV will then display a waveform when I speak, beside the amber dot that indicates the mic button is being pressed. But if I land on the language that does not precisely correspond to Siri's supported list, that prompt will not show, and pressing the mic button will have no effect when the prompt is on the keyboard.
Unfortunately, this is where semblance of similarity ends. Key points:
- Even as the "Dictate" function is impaired because of the language mismatch between keyboard language and Siri support (Settings still shows Dictate" as "ON"), Siri continues to work as designed in the selected Siri Language. When I press the mic button, an amber dot appears on screen; then when I speak, a waveform is displayed beside the dot.
- During those "silenced" episodes, the amber dot appeared with both Dictate and Siri whenever mic button was pressed; in Dictate mode, the "Press 🎤to dictate in XXX." prompt appeared, too. But no waveform was displayed when spoken into - rather, there was a flat line.
- During those "silenced" episodes, switching language had the same effect on appearance and disappearance of the "Press 🎤to dictate in XXX." prompt and of the amble dot as in normal times. The only difference is whether waveform appears when the mic is spoken into and whether Dictate and Siri responds.
So, I do not think that the "silenced mic" problem is caused by language selection in on-screen keyboard.