How to play one-channel audio in both headphones? I would like to have exactly the opposite of this question, or this.
Some audio documentaries on youtube that I want to listen to with an old-style (wired, non-bluetooth) headset have only one channel audio. That is, I hear audio in just one ear.
Is there a way to hear the sound in both headphones while playing that? (That would improve the experience, the voices are not always clear, etc.) — I mean, maybe there is an app that has a setting for that.
NOTA BENE:
I am referring to wire headphones here, not bluetooth. The device is Xiaomi A2 phone running Android 10.

EDIT after comments:
Opening the audio file in Audacity, I see this:

Although Mediainfo says 2 channels:
Two of the comments made by @AndrewT have suggested to me the good solution:

true mono audio shouldn't be a problem when played on stereo speaker
(it will play the same waveform on both left &amp; right channel)

and

the audio source is actually stereo, but the audio is only recorded on
1 channel

As the youtube audio in question is not a mono but a stereo with just one channel (Audacity was right, Mediainfo was wrong), a solution is exactly the one that initially seemed to me the opposite of what I wanted: rendering the file as mono — and thus, playing it through both headphones.
This solution works on Android 10, the setting is under Accessibility, Audio&amp; on-screen text.