If an iPad has its language setting to “English (Australia)”, certain keys like the dash (-) don’t work in Obsidian (but work fine in other apps). This is true for both the on-screen keyboard and a separate physical keyboard.
It works fine when the iPad keyboard settings are switched to “English (US)”.
I don’t think this happened when I started using Obsidian a couple months ago, so may have broken in a recent update.