Use Unofficial Remote Patch for change key.xml for example 3D key to screenshot
https://www.futeko.com/newforum/index.php?topic=1259.0
Edit on key.xml
<key value="0xae51ef10" name="KEY_3D" />
to
<key value="0xae51ef10" name="KEYCODE_SYSRQ" />
or via adb shell from PC
adb connect <ip_player>
adb shell input keyevent 120
PS: KEYCODE_SYSRQ = 120