Google has a Google Assistant app for Android, iOS and Chrome OS, but nothing for Windows 10.
This is a gap developer Melvin Abraham decided to plug, with his release of the Google Assistant Unofficial Desktop Client for Windows 10.
The app is open-source and available on GitHub, but unfortunately despite appearing pretty slick, is not quite ready for prime time yet.
Specifically, it takes about 30 steps to install the client, including registering for a Google Cloud account.
Based on Electron, if you are determined enough you end up with an app which takes voice or text commands, supports most Google Assistant features, has Dark and Light Mode, built-in updater, and even has hotkey support.
Always listening mode is however absent and Continued Conversation is a bit patchy and 3rd party integration such as Spotify and Netflix does not work.
If that does not discourage you, you can check out the project, which will likely improve (until Google bans it) at GitHub here.