Quite often (I cannot reproduce it, but it happens every time I use the iOS version of Brave), the on screen keyboard closes immediately when I open up a new tab and/or try to type in the address bar. Once it occurs, I can try as often as I want, every time I want to type on the on screen keyboard, it closes quickly before I can type anything.
Workaround: I have to push the home button and reopen the Brave browser (sometimes repeatedly), until the onscreen keyboard stays open.
System: iOS 12, newest version, Brave for iOS, newest version, iPhone 8 Plus.