Bug Report from one of our internal engineers working on the tracked keyboard feature:

"Recently encountered this Unity bug while upgrading the tracked keyboard sample. I made a minimal Unity project to repro it, shown below. When I type, nothing occurs. It only affects Unity UI input fields, the Input.GetKey() call still works normally.
• Text appears normally: 2020.3.31f1, 2020.3.33f1
• Text does not appear: 2020.3.34f1, 2020.3.35f1, 2020.3.36f1, 2020.3.37f1 (latest)
• Works fine on 2020.3.34f1 in PC VR (Link) when using regular USB keyboard
• Test project was created from scratch in 2020.3.36f1, there are no C# scripts in the app and all properties are set to default. The EventSystem is set to give initial focus to the input field
Notes:
• I tried both the Logitech K830 keyboard and Apple Magic keyboard.
• I tested on Quest 2 and on Cambria and on my personal Quest 2 which is running a live OS build (v42) No difference.
• I can type normally in Shell (and in v2020.3.33f1) and the Windows key still calls up the system overlay.
• I verified that the Inspector properties of Input Field have not changed between versions.
• I verified that downgrading back to 2020.3.33f1 stops the issue from occurring.
• It is possible that this is by design and there has been some change to default settings or something that I am not aware of.
• I have not yet tested recent versions of Unity 2019 and Unity 2021.
TESTING
2020.3.34f1 was released on May 4 so this issue has been public for almost 3 months. Most devs probably haven't encountered it because they either don't use Bluetooth keyboards or don't upgrade Unity that often, but nevertheless, it would've been good to detect it faster."