I recently got a bluetooth keyboard and mouse to be able to play Minecraft with keyboard and mouse on iOS (since support was added in 1.19.10). However, the mouse does not properly function. I cannot press play, settings, or any other buttons on the home page. I cannot open worlds using the mouse, or, really, interact with the UI at all. The mouse does not work with inventory. The only things it works for are breaking blocks and attacking mobs (with left click), and using items or interacting with objects (with right click). This is a pretty serious problem since I’m playing on keyboard and mouse, but to use any UI buttons, including inventory, crafting, etc, I must touch the screen with my fingers, which defeats the purpose of using a mouse.

Note: I've heard from people that kbm works on iPad, but its definitely broken on iPhone. On the bug report video, which is linked below, people have said in the comments that they are having similar issues, so its not just me or my device (Which is an iPhone 11]. My brother, who has an iPhone 8, also has the same problems, so its not just device-specific: I'm updating this issue because the bugs were not fixed in 1.19.20, and a new bug has appeared.

Full list of the bugs known to me:

-The Mouse is unable to be used in menus such as the startup screen, settings, and any other menu.

-You cannot use the inventory with the mouse. I.e: You can’t select items, put the items in the inventory, craft, or do any other mouse functions in inventory. You HAVE to use your fingers (which defeats the purpose of having a keyboard and mouse to play).

-The iOS mouse cursor does not stay centered on the screen during gameplay, but instead goes all around the screen.

-As a result of the last bug, the mobile controls flash onto the screen if you click while the cursor is on certain parts of the screen (this does not happen every time, but it seems to occur most often when the cursor is at the edge of the screen).

-The Chat seems to be broken. Every time you press shift or caps lock to capitalize a letter or add a punctuation mark, the chat box is no longer highlighted, and you cannot type inside until you tap it again.

-Sometimes with the chat, pressing enter on the keyboard does not send the message, but makes it so you cannot type inside it.

Now for the bug that has happened in 1.19.20:
-Since players have to use fingers for inventory and menus, the mobile controls do appear on the screen. In 1.19.10 and 1.19.11, you could simply move the mouse and continue playing, but in 1.19.20, you now have to drag your finger across the screen and then click for it to work (this isn’t always necessary because sometimes it functions like in 1.19.10 and 1.19.11, but it is needed most of the time.

Steps to Reproduce:
Most of the bugs are reproduced through regular gameplay.

1) Upon starting up the game, you will notice that the mouse cursor has no effect on any of the UI buttons. You cannot press play, open settings, go to the Marketplace, or anything else. Similarly, you will not be able to click on worlds to open them.

2) To recreate the inventory bug, simply open the inventory and attempt to grab items or craft stuff.

3) When you enter a world, move the mouse around, and you will see that the cursor is not centered on the screen.

4) The best way to recreate the bug where the mobile controls appear is to arrange the cursor over the hearts in the upper left corner, and click repeatedly. It may not happen, because as I said, it does not happen every time,

Since its a brand new feature on iOS, I understand that there are some bugs, and I hope that Mojang will be able to fix the bugs in later updates.

P.S: Here’s a link to a video that addresses this exact issue
Keyboard & Mouse control bug in 1.19.10 on iOS-Bug Report
https://youtu.be/ISmijWKb5C4