--keep-awake flag doesn't seem to work on some phones, even when wired

[ArtyIF]

• I have read the FAQ.
• I have searched in existing issues.

Environment

• OS: Arch Linux
• scrcpy version: 2.4
• installation method: pacman, official extra repository
• device model: realme 12+ 5G (RMX3867)
• Android version: 14 (realme UI 5.0)

Describe the bug
When trying to connect to my phone over USB with the --keep-awake flag, an error occurs when scrcpy tries to change the setting, making the flag useless. Log output:

[artyif@artyif-desktop ~]$ scrcpy --select-usb --no-audio --turn-screen-off --stay-awake
scrcpy 2.4 <https://github.com/Genymobile/scrcpy>
INFO: ADB device found:
INFO:     -->   (usb)  <serial number>                device  RMX3867
/usr/share/scrcpy/scrcpy-server: 1 file pushed, 0 skipped. 119.3 MB/s (69007 bytes in 0.001s)
[server] INFO: Device: [realme] realme RMX3867 (Android 14)
[server] ERROR: Could not change "stay_on_while_plugged_in"
com.genymobile.scrcpy.SettingsException: Could not access settings: put global stay_on_while_plugged_in 7
        at com.genymobile.scrcpy.Settings.execSettingsPut(Settings.java:24)
        at com.genymobile.scrcpy.Settings.putValue(Settings.java:59)
        at com.genymobile.scrcpy.Settings.getAndPutValue(Settings.java:78)
        at com.genymobile.scrcpy.Server.initAndCleanUp(Server.java:75)
        at com.genymobile.scrcpy.Server.lambda$startInitThread$2(Server.java:206)
        at com.genymobile.scrcpy.Server$$ExternalSyntheticLambda0.run(Unknown Source:4)
        at java.lang.Thread.run(Thread.java:1012)
Caused by: java.io.IOException: Command [settings, put, global, stay_on_while_plugged_in, 7] returned with value 255
        at com.genymobile.scrcpy.Command.exec(Command.java:16)
        at com.genymobile.scrcpy.Settings.execSettingsPut(Settings.java:22)
        ... 6 more
INFO: Renderer: opengl
INFO: OpenGL version: 4.6 (Compatibility Profile) Mesa 24.1.1-arch1.1
INFO: Trilinear filtering enabled
INFO: Texture: 1080x2400
[server] INFO: Device screen turned off

The phone doesn't have a caffeine QS tile, as someone has suggested in a different issue, only the "Keep screen on while charging" setting in the developer options.

[rom1v]

Duplicate of #4021.