A low cost option is to use the live transcribe that is embedded in apple phones. I have a family member who uses this in conjunction with hearing aids. It isn't discrete but it helps her out - especially in larger conversations with many people.
FWIW it is far from perfect but it is helpful - and better than any paid apps that we've encountered.
The android default "live transcription" app works pretty well for that use case too, but its main flaw is that it uses the phone's microphone.
This may be a stupid question, but what's the flaw? Surely transcribing audio requires a microphone?