How can I turn this off? All the posts I see basically conclude with "get a better power supply".

Yes, yes, I know you are not supposed to do this, I know there are risks of an unstable system. It's my device. If i want to run it with low voltage that's on me. I won't come back here crying if it breaks.

Can anyone tell me how to disable this annoying pop-up in Raspbian?

I recall the only option was to recompile the kernel and take out the checks as low power is considered an absolute "fault condition" by Raspberry Pi.

It's in a thread somewhere.

I can't help with that, but it is ironic that it is probably going to be easier to just get a proper PSU...

remove 'power' from the panel. right click panel -> add/remove

Yes, I know this post will attract the expected blowback.

But I get where OP is coming from. The low power signal often comes even though:

1) You have the "recommend" power supply
and
2) It really doesn't hurt anything

My posts may be "controversial" and/or out-of-sync with the party line.

Nothing I write should in any way be taken as an official statement by any organization connected with (any branch of) RPi and/or any of its funding sources.

The issue comes down to using a binary indicator to report on a multi-state system - The problem being that the low-voltage indication arrives at a voltage where the under-voltage is not severe enough to compromise operation. It's perfectly fine other than having that low-voltage indication.

I view the low-voltage indicator like the low-fuel indicator in a car; a warning. You can drive forever with the low-fuel warning light on with no damage done if you keep adding fuel. It's just a warning that you may be heading in the direction where things won't work as desired, where damage may be done.

Raspberry Pi disagree, considers low-voltage an absolute fault condition which must be rectified, even if your Pi is perfectly fine at that voltage.

And that's how it is because they make the rules.

The low voltage warning threshold is the voltage below which we cannot guarantee reliable performance.

Software guy, working in the applications team.

yes, even when you think it works fine, at the same time it might corrupt your sd-card content! so don't gamble it wil be fine,, and later complain that it doesn't boot "just like that".

S can happen under any circumstances. I don't think there's any particular reason to single this one case out.

My posts may be "controversial" and/or out-of-sync with the party line.

Nothing I write should in any way be taken as an official statement by any organization connected with (any branch of) RPi and/or any of its funding sources.

I recall the low-voltage warning is set at about 4.6V for the 5V rail, though the exact point varies by product and revision and of course the manufacturing tolerances of the monitoring chip.

The SoC, SD Card and other 3V3 supplied components should work as expected so long as they are powered by 3V3, so long as the voltage into the regulator or PMIC is high enough for it to supply that 3V3.

I don't see how the SoC, SD Card or any 3V3 component supplied with 3V3 could or would be damaged, would fail or behave unexpectedly, under those circumstances.