For the foreseeable future, at least, the most interesting things that emerge from asking the question "What came before the Big Bang?" is a lengthy discussion about what "before" even means. Since time, as we understand it, is held to begin with the Big Bang, the question may not even make any sense -- although even nonsensical questions are worth asking, if doing so gives you an opportunity to learn why you shouldn't have asked it. In this case the point is that time is not necessarily infinite, in either direction, and nor does it have to be linear. Or even "universal"; although the differences are virtually non-existent, you and I measure time in different ways. Indeed, your head and your toes don't even experience time in the same way (https://www.newscientist.com/article/dn19494-standing-on-a-stepladder-makes-you-age-faster/ ). All of which makes "before" a woolly notion anyway, before going to the extreme conditions of the Universe at the time of the Big Bang.
My best guess is that the question of what came "before" the Big Bang is likely to remain unanswered. Hopefully people won't be discouraged from trying, for sure. The problem is that the Big Bang is, presumably, something we can't replicate in a lab and something that we can't really probe "beyond". On the "other side" of it, if there is one, there wouldn't even be a guarantee that the same laws of physics as in our Universe would hold (although, presumably, they would be at least fairly similar).
Perhaps, with the recent direct detection of gravitational waves, it won't be long before their detection is also confirmed in the Cosmic Microwave Background radiation (reported a couple of years ago, but since retracted, so we're still waiting for it). That, I think, would help to push the threshold of times we can observe from 380,000 years or so after the Big Bang to maybe a few seconds, or even fractions of a second. The closer we can get to observing the Big Bang itself, the better chance we would have of understanding its nature, and in turn what, if anything, came "before" it.
Until then, the best we can do is speculate. It's pretty fun, though, and the speculation can help to drive a greater appreciation of what we *do* know.