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Magic SysRq

Enable Immediately (Temporary):

sudo echo "1" > /proc/sys/kernel/sysrq

Enable Permanently:

echo "kernel.sysrq = 1" | sudo tee /etc/sysctl.d/99-sysrq.conf
sudo systemctl restart systemd-sysctl.service

Verification: Check if it is enabled by running cat /proc/sys/kernel/sysrq. A value of 1 means it is enabled.

The "REISUB" Method (Safe Reboot)

This is a "backdoor" into the Linux Kernel that bypasses the frozen display and tells the hardware to shut down gracefully.

Hold down Alt and the SysRq key (usually the same as Print Screen).
While holding both, type the following letters slowly (about 1 second apart): R — E — I — S — U — B

Used Keys:

r: Switch keyboard from raw mode to XLATE mode.
e: Send SIGTERM to all processes.
i: Send SIGKILL to all processes.
s: Sync all mounted filesystems.
u: Remount all filesystems read-only.
b: Immediately reboot the machine

One more "Soft" trick

Before doing the REISUB reboot, try switching to a TTY (Terminal). Sometimes the graphical interface is just "stuck" on a black frame:

Press Ctrl + Alt + F3.
If a black screen with text appears asking for a login, your system is fine! You can just type sudo reboot there.
To go back to your desktop, press Ctrl + Alt + F2 (or F1).

6th-Gen Intel "Wake Fix"

Since you have an Intel 6th Generation (Skylake) CPU, you are hitting a very specific, well-documented issue with the i915 graphics driver's power-saving features.

On this specific generation of Intel chips, two features called Panel Self Refresh (PSR) and Display C-States (DC) are notorious for failing to "wake up" the screen, even if the rest of the computer is running.

Open your terminal and edit the GRUB file again:

sudo nano /etc/default/grub

Find your GRUB_CMDLINE_LINUX line. It currently looks like this: GRUB_CMDLINE_LINUX="rhgb quiet acpi_osi='Windows 2020' i915.enable_psr=0 i915.enable_dc=0"
- What these do: > * i915.enable_psr=0: Disables "Panel Self Refresh," which often gets stuck in a "blank" state during wake.
- i915.enable_dc=0: Disables "Display Power C-States," preventing the GPU from entering a sleep mode it can't exit.
Apply:

sudo grub2-mkconfig -o /boot/grub2/grub.cfg

scrcpy

scrcpy -m 1024 -b 2M --max-fps 30 --no-audio

-m 1024: Max width
-b 2M: Bit rate
--max-fps 30: Max fps

Acer hidden boot entries

Video