UPDATE:
I was wrong on one extender, I did get it back online by simply power cycling (several times?).
The other extender is still dead but I got a message saying a device was ready to ship out, so it's all good so far.

I've contacted Google and they will only replace one of the extenders "at a time due to security concerns".
Regarding the extender failures, I have no idea. I've checked the power supplies and they are still outputting 5.0 vdc and I successfully pulled 2 amps from both.
But both extender units will not light up at all - they are warm, showing they do "see" the incoming power but they do not respond.
It's my opinion that it was most likely a bad firmware update that bricked them. I asked the google tech and he said that info was above his pay grade.
But he didn't question be at all on details, I described both units dead and he immediately said they'd ship out a new one. Once I get the new one online, then they'll ship the second one. Whatever.

I'm an old guy who rarely uses the garbage disposal and I never put food down the drain. So it's been relatively clean and smell free.

But my mother's house has a nasty dirty garbage disposal and why wouldn't I just take that out instead of replacing it?

I think just a drain strainer and being normally cautious with not putting food down the drain would be just fine.

As a side note, when I helped manage some school buildings, the plumbers hated the garbage disposals. But teachers were also terrible. They'd put everything down the drain.