The Firefox Focus browser is available on the iPhone and I see is at Google Play. It is a standalone browser and blocks ads. If you download it on the iPhone it also shows as an extension in the settings for Safari. You can flip the switch to use it there. I think it doesn't show the content of embedded tweets, and there doesn't appear to be a setting to allow this. But clicking where you see the tweet would otherwise appear, takes you to the tweet.
As a standalone browser, I think you have to log in to CF every time you start it up. But you don't have to log in necessarily just to read the threads.