Comment by command_tab

I've had great success doing transcription on-prem with Speechmatics: https://www.speechmatics.com They offer both a VM and a Docker image that you can run behind your firewall, and even license offline if you really need to. I use it for generating closed captions of videos, but you could build a transcription tool out of it as well. Their engine's accuracy is the best I've found out there, too, which is a nice bonus.