Not saying they had electric lights. I'm saying it's feasible. To be considered better than fire, could be simply you don't suffocate when you use it in a tunnel because it doesn't use up all your oxygen. They were also obsessed with cleanliness. Burnt remains is not clean. An electric source could also be seen as holy or magical and not-of-the-earth. There are many reason it might have been used even if it gave off less light than an open flame. If they used some oil that left no residue, we're equally unable to find that or explain what they used there. That's an equal leap of no evidence. Copper would have been far less expensive than all the gold they had in those tombs and based on the size of the pyramids cost wasnt a huge concern.
Yet there's clear evidence of soot in tombs and there's fairly easy means of ventilating tunnels etc as well. There's millennia of lamps and such going through some of them. The issue is simply this. Go get a 0.6 to 1.4 v battery and connect a filament and see if it will glow. It wont. If you go look up the so called Baghdad battery you'll see Iron in it which Egyptians didn't have and the way its seals would prevent anyone from connecting the two terminals. Finally the most important is every actual bit of evidence from actual archeology suggests that the pharaohs put food and drink in their tombs for the after life and it was considered as per real.life. therefore if these lights existed surely there.would be a few examples in tut's tomb alongside the huge amount of evidence in his treasures. There's jars in there for oils etc that long since seeped away. There's an alabaster oil lamp that's really quite fancy that has traces of oil in it and salts as well that reduce the smoke. On the other hand there's literally zero evidence to support electric light as I doubt you can show an image that looks anything like one. Here's a good one.... if there's no air in said tombs while they are being decorated to support a lit candle then how was there air to breathe at all. The depth of some tombs in the valley of the Kings would take an hour to go down
Egyptians did have iron, but it was very rare. Iron shows up several places in history before the iron age. Iron daggers have been found in pharoahs tombs. They certainly didn't have advanced or widespread knowledge of iron producing though and most pre iron age iron would have been sourced from meteorites... Which are pretty rare. I agree that no such objects being found in a pharoahs tomb would count against the theory. Comparing it to modern incandescent light bulbs is a bit of a red herring because obviously they couldn't have used same technology we did, they didn't have the same alloys available. . As for oxygen, of course there had to be some oxygen deep in the tombs to breathe, but naturally you would want to avoid using it up. Even salted oils do leave soot behind, just less, and there are chambers with no detectable soot deposits. It could be that 3000+ years and minimal time possible spent in a tomb will do that. Time erases things.
Webb Telescope Shatters Distance Records, Challenges Astronomers - Sky & Telescope - Sky & Telescope (skyandtelescope.org)
Several times by several different scientists, yet still remains the most accepted. My personal favourite theory is the the big bang has always been happening and will always be happening... Like a curve to infinity in either direction of time. It's more a poetic reason I like that theory more than any scientific basis why I like that particular theory the best...