Would like to write my emails using voice. I daily reply to many emails and I write quite a lot of text each day. To stop carpal pains, or reduce their occurence, I would like to dictate as much as I can to reduce keyboard use.
Discounting Android and it's accompanying Google software, there's not enough of a user base on desktop distros combined to attract serious development efforts.
Siri is apple so.. probably never, you will have more hope with Alexa since it's Amazon product and that isn't actually tied to specific hardware as such.
and also some tinkering has been done with alexa:
https://www.iotforall.com/how-add-alexa-raspberry-pi/
I've not tried either myself since I'm still stuck on windows but until either original does stuff with linux (totally unlikely with Siri, although apple is 'nix based) you might want to look at alternatives.
If you switch to Windows, there're quite popular voice-recognition applications (paid). As said above, switching to Android (it has voice-rcognition) and your language is supported, is another option. Various websites claim Siri is available on MacOS as well.
As for Siri or Alexa on Linux (or Windows) - I would not hold my hopes high.