Note I am on an iPad Pro 12.9" Gen 1 on iPadOS 13 using MCBE version 1.12.1. I don't know if this bug is iPadOS exclusive or if it effects iOS as well.

What happens: When downloading a resource/behaviour pack from an online resource, when you tap on said download from where ever you tap it from, (whether it's Safari's built in downloader or in the Files app itself,) the download will open Minecraft but will 100% always fail to import.

What's supposed to happen: When you tap on a resource/behaviour pack downloaded it should open Minecraft and import fully without any movement of files, (I'll explain later.) This used to happen either prior to 1.12.X or before iPadOS 13 came out, either one of these updates could have created this issue and I'm not sure which. I have no way of figuring out which one is it though as both Minecraft and iPadOS can't be downgraded to test.

How to recreate: Find any resource/behaviour pack online that will work in the game on the current version of Minecraft. I tested it with this resource pack and it works on 1.12.1. Download it then tap on the file to boot up Minecraft and to attempt to install. It will say something like, "failed to install resource/behaviour pack." The resource/behaviour pack will not be installed.

How to fix: You have to open the Files app and find the download of the resource/behaviour pack, (usually it's in Downloads on iCloud Drive,) tap and hold, copy, then go into "On My iPad", open "Minecraft", (note that from here on out the app may be extremely laggy and may even crash. Be patient and careful. Making a mistake editing the games files without knowing what you are doing could result in your game being broken and critical data such as entire worlds to be lost.) Open "games", open "com.mojang", then open either "behaviour_packs" or "resource_packs" depending on what you downloaded. When in that file tap and hold then paste the downloaded file, once it has been pasted, tap on the download to open Minecraft again, while inside said file, and then wait for it to download. It will work now like it usually would.

If there are any questions or clarification needed, please comment. This issue isn't huge by any means but it is extremely dangerous as it forces people to go into the games code to add resource and behaviour packs. This is how it's done on Java but the Bedrock userbase, espiccialy the userbase of the iOS and iPadOS versions is much much younger and far more prone to destroying their game while editing critical game files.