https://github.com/w3c/IndexedDB/issues/230
I personally think that this stall is simply a symptom of the larger issue that the IndexedDB standard was bad to begin with, and that lead to lax adoption from developers, which deprioritized vendors from fixing the standard, leading to a vicious cycle where even a seemingly trivial issue like adding BigInt support goes unimplemented.
I personally think that IndexedDB is salvageable, and not only that, it has the potential to be an amazing web API. But the way things are progressing with the standards committee, I very much doubt it will be any better in the foreseeable future.