Unfortunately, I have already undertaken the steps you have mentioned. I have disabled the Realtek audio chip in my motherboard's BIOS, and disabled all other input sources except for my microphone in Windows sound settings.
My headphones and microphone are already separated, so there should be no conflict there either. I believe this is an issue with the game and not my hardware setup, having removed all possible sources of confusion.

I am unable to attach the error.log file as it trips the website's security blocks, but these are some logs from a session last week.
For Prototype, you can find these logs in Documents/My games/ArmaReforger/logs.
If there is anything else you need, please let me know.

I have also discovered that toggling app microphone access in Windows privacy settings will temporarily fix the problem too.