Unfortunately certain iPhones do not have MutationObserver support. This is not the case on newer ones. There's an open bug to allow you to opt out of this how

Unfortunately certain iPhones do not have MutationObserver support. This is not the case on newer ones. There's an open bug to allow you to opt out of this however we've been a bit stretched to find the time to work on this. https://phabricator.wikimedia.org/T261609 https://phabricator.wikimedia.org/T261609