Is there any keyboard which lets you configure the service used for voice input?
I’d like to set an URL to a selfhosted service to send my voice to be processed which then will return the transcription.

If no keyboard exists for this any app would do.
The idea is the app lets you stream the audio to the given service and will receive the response and show it for you to edit, similar on how google keyboard has the voice input.

Bonus points if it’s open source :P