(no audio process experimentation in Mac M71 stable so far)

I believe this is a case of Chrome not having the correct system-level permission to access the microphone. It's a new permission added in macOS Mojave (10.14), so I expect it would've broken during that upgrade.

To fix it, go into System Preferences -> Security & Privacy -> Privacy -> Microphone and ensure that Google Chrome is checked.

If this fixes your problem, could you tell us more about how you moved to macOS 10.14? Sounds like it was a regular upgrade. The OS is supposed to ask the user for the permission when Chrome tries to open the microphone for the first time, but I've seen this problem reported enough times that I'm beginning to think something's gone wrong at the OS level.

Great. That was ultimately the problem and haven't even thought in looking into that panel. 

By having restored the settings and having seen Chrome asking for using the microphone (it did in fact asked again once more now), I would have expected that level of check being already done from the browser itself? Perhaps something to implement?

That said, yes it was a regular update via the AppleStore. 

Good to hear that that solved it!

The dialog asking for permission cannot be shown again by the app once permission has been denied. There is work planned to deal with this better, though.

I think there is a kind of misunderstanding here. Let me elaborate.

At any time when the Mojave has been installed, I never been proposed for a panel that could have lead me to think settings were going to change.
On the contrary, in visiting new sites where microphone was required, I got the pop-up asking for such authorization. Despite the grant, I couldn't get the microphone though. This happened in a recent hangout via Google Meet.

That's why I believe many users are confused. Because they primarily look into the browser settings, but they don't expect Chrome being disabled at OS level.
Although, it's fairly strange that in installing a fresh Canary version yesterday, such settings have been granted without anything additional.

So my suggestion is to check whether that setting is somehow on/off when a new site is asking for that permission.
Also, it would be great doing the same when browser settings are restored.

Hope that makes sense.

Thanks for the clarification.

I agree Chrome should do a better job of informing the user of this, even if it cannot actually change the permission itself. That's part of what the bug I duped against is about - I'll see if I can push it along some.

It sounds like the system pop-up asking for this permission never appeared for you, is that correct? Have you had the same issue with the camera, or was that working fine throughout?

Actually, when I jumped on Google Meet I was asked for the microphone grant (because I was not using it since a while anywhere).
Equally, after having reset all the permissions, I was asked again. But, as I said, no joy.

I actually thought this was a problem of Google Meet, though even a couple of plug-ins were not working (which is when I start getting suspicious). Ultimately, testing also WhatsApp and loads of other things lead me to the problem being with Chrome and not with the app themselves.

Camera always worked fine immediately.