Ubuntu Desktop 20.04.1 LTS shows corrupted display after system boots up

[Wayne Chen]

Description:
Ubuntu Desktop 20.04.1 LTS can boots up and user can log in successfully, but only the upper half of the screen shows desktop, the bottom half displays pitch black.

Reproducibility:
Constantly

Steps to reproduce:
1. Setup extended display with another display connected to USB
2. Adjust and apply display resolution in both original and extended display
3. Disconnect extended display by plug it out directly
4. Reboot system and login
5. Check original screen

Expected Results:
The original display work as normal and as before

Actual Results:
Only the upper half of the original screen shows desktop

Environment:
Ubuntu Desktop 20.04.1 LTS with kernel 5.4.0-52-generic
Dell XPS 15 laptop:
https://www.cnet.com/products/dell-xps-15-laptop-dncwxb1641sv2/
Dell 4K Monitor:
https://www.cnet.com/products/dell-p2715q-led-monitor-27-p2715q/

Logs:
uname -a
cat /etc/os-release
lscpu
Lspci
lsusb
dmesg
journalctl —system
/var/log directory

Any further detailed logs can be obtained by using apport-bug or ubuntu-bug