I have installed AospExtended's official build for my device last night, since then I'm unable to launch the recent apps menu. Through deep investigation, I found that there exist settings to customize it but it won't launch.
Has the method to launch "Recent Apps" menu been changed in Oreo? This is the link to my rom: https://downloads.aospextended.com/tomato
Also, I have installed minimal Open Gapps through
aroma since my system partition wasn't necessarily big.