The people at Opera really want you to use their browser. That's been true for over 25 years, but today they'd really like you to use Opera on Chrome OS. If that seems a bit incongruous — "Isn't the entire operating system the browser?" — what they mean is that the Android version of Opera has been optimized for Chromebooks and other Chrome OS devices. You can install it via the Play Store.
Opera's blog post on the topic touts the browser's typical all-in-one approach, with support for the most popular messaging clients, a built-in ad blocker, a VPN, a cryptocurrency wallet, and a huge collection of themes. But the biggest of deals is that its interface is actually designed to be used on a laptop or tablet, which is more than you can say for most of the Android browsers available to install on Chromebooks. Indeed, running a quick test, it's initially hard to remember that you're technically running software that's the same code as it is on an Android phone. It's a big improvement over, say, Brave running on a Chromebook.
That said, I can't help but feel like Opera is patting itself on the back pretty hard here. While the interface looks great on my Pixel Slate, it doesn't take long to spot the differences between the Android version of Opera and a true desktop browser. There's no support for extensions, you can't open multiple windows or click-and-drag tabs into new ones. As an Android app, you can't control it with many of Chrome OS's shortcuts. Even the text and image scaling seems off, like a giant phone still formatting the interface for a tiny screen.
I suspect that the biggest draw here is that long-time Opera users can use Flow, Opera's tool for syncing accounts and web history, on Chrome OS. But if you're such a dedicated Opera user that you desperately want to use it on every single device, I think an equivalent Windows laptop will still probably be a better choice for you than a Chromebook.