Downloading
Your download is starting.
If nothing happens, download Uttrflow directly.
Or install with Homebrew
brew install --cask uttrflow/tap/uttrflow
The app updates itself after that, so there is nothing to run again. You still need the command below the first time — Homebrew quarantines what it downloads and has no way to skip it.
Once it lands
Open the disk image and drag Uttrflow to your Applications folder. The first launch asks for the microphone and for Accessibility — the second is how the words get typed into whatever you were already using.
Uttrflow is not notarised by Apple yet, so macOS has not been told to trust it: it will say the app is damaged, which it is not. Once Uttrflow is in your Applications folder, however it got there, run this once in Terminal.
xattr -dr com.apple.quarantine /Applications/Uttrflow.app
Then sign in. Uttrflow needs an account once, on first run; after that it works with no network at all.
The app is open source under the MIT licence. If you would rather read it than trust it, the code is at github.com/uttrflow/uttrflow-swift, and it builds and runs without an account or anything of ours.