Usable on google chrome?

Is proton VPN usable on google chrome?
If so how do I use it on Google chrome?

Yes.
The easiest way to utilize ProtonVPN is to download the program and utilize it that way. It will route all of your computer’s traffic through the VPN network including yoir browsers.

Chrome os or chrome browser?

If chrome os just use the play store app. Works great for both android phone and Chromebook/chrome os devices.

Is this VPN trustworthy?

Thanks, do I need to do anything after connecting to a server?

No, once you’re connected restart chrome and you should be fine. I’d clear cookies on chrome after connecting to the VPN. Further, I think Proton said they’re working on a browser extension as well but I think that’s still in development.

I guess, for now stick with the application.

You don’t need to restart any apps. This will happen as needed in the background.