How to reproduce:
1. Open "ChineseInput" project (Make sure your OS keyboard language is set to Chinese)
2. Enter Play Mode
3. Write some text in the Input Field in the Game view
4. Exit Play Mode
5. Go to Window -> Package Manager and install Input System
6. Select the EventSystem GameObject
7. Press the "Replace with InputSystemUIInputModule" button in the Inspector
8. Repeat 2-3 steps

Expected result: Chinese text can be input
Actual result: Chinese text cannot be input

Reproducible with: 1.0.0 (2019.3.14f1, 2020.1.0b9, 2020.2.0a11)
Could not test with: 2017.4.40f1 2018.4.23f1 (New Input System was not supported)

Note: Chinese was used as an example, but other languages (Japanese, Korean) are also blocked.