Can we have an open source Google Assistant alternative?

What if we use the Google Speech utility to make it work?

I'm tired of apps not integrating themselves with Assistant.

I use Microsoft To-do for work. And I have a Windows device so it's extremely convenient for me since it syncs it.

But when I ask Google to add a task, it won't do that. (Refer to the attached image.) It will only add tasks or reminders to its own shitty Tasks app.

So, I want to be able to automate my work by having some service that can do this, and doesn't have to depend on Assistant or the devs to add Assistant compatibility...