This is addressed on the Github issues of the Kivy Project:
https://github.com/kivy/kivy/issues/6563
The Tipp from KiaraKarla:
kiarakarla commented on 15 Dec 2019
We are not likely to release a 1.11.1 version for 3.8 to pypi. However, you can install kivy master using pip install kivy[base] kivy_examples --pre --extra-index-url https://kivy.org/downloads/simple/.
Worked for me to get kivy working with the Sample under Win10 with Python 3.8.2