James Webb Telescope is getting closer to finding what ionized the universe
The results are not conclusive, however, because of the number of assumptions that the astronomers had to make. But it does point in an intriguing direction in solving this long-standing cosmic riddle.
https://phys.org/news/2023-03-james-webb-telescope-closer-ionized.html
Paper: not yet available
Yep.
Then there is the very problematic "Inflation" theory.
That only exists to try and solve the Flatness issue with the Big Bang.
Readings: (that don't address the Big Bang directly, but point to why it might not be needed.
https://tritonstation.com/2023/02/20/imagine-if-you-can/
and