LED bulb won’t work in a standard outside porch light fixture
Given the symptoms, I have to suspect that this fixture is wired with the bulbs in series, rather than with the bulbs in parallel.
So, two incandescents - operate happily if somewhat dim and yellow on half-voltage. Bulbs would last a long time and veer towards &quot;bug light&quot; yellow without the ugly yellow paintjob, so it's not unreasonable for a &quot;porch light&quot; fixture.
One LED one incandescent - adequate voltage for the LED, so little current you don't even notice the glow on the incandescent.
Two LEDs - half voltage, ain't nobody happy.
Diagnostic - one bulb, one empty socket - what happens?