Except you can't. Every browser on iOS uses Safari's rendering engine. Chrome/Firefox on iOS are effectively reskinned Safari. This is an apple requirement. The rendering engine being the important part here when talking about standards and such.
Every time this discussion happens a non-trivial number of people reveal they’ve fallen into this trap of believing other browsers are allowed on iOS. Feels like a consumer protection issue, at some level.
I tried Orion (m1 MBP) recently. From about 3wks ago til a few days ago. I liked the UI. But there were a lot of pages that didn’t work correctly. I persevered for a while. But gave up a few days ago and went back to Brave.