Samsung got my phone roughly December 23, 2020. Currently it says it's under investigation. How long is the process to investigate, fix and send it back to me.
It depends. I recently had the ECG sensor in my watch replaced and it took 3 business days to be investigated, fixed, and sent back. Your phone might take a bit longer because of upcoming holidays and weekends, but you should expect it to be done within 5 business days.