I have tried Dicio but it requires network access and is fairly limited (at least as an app if you're not a dev). I've looked around and can't get an install anywhere for Athena or Saphire which appear not to be in active development.
I've looked at Kalliope also, but this requires a server / service locally ... not the end of the world, but I don't have access to my personal server all the time. This is due to upload bandwidth constraints, so mostly I'm connected to the world via VPN over 4G or via the work network which is fast unless I need to access something on my LAN.
Google Voice Access doesn't require any Google services to run and works extremely well. It works without installing the 3 sandboxed services, but does require network access. They 'say' you are opted out of sending data for product improvement ... but, they aren't exactly a reliable witness.
Is this 'safe to run' ... or I'm defeating the purpose?
Note, happy to take advantage of Google if it makes sense.