@webkitdevtools Oh, sorry, I thought it will launch with the original Safari application. Tested with the separate "Safari Technology Preview", it works now. I can see all the tabs with iOS simulator. Thanks for help. May I ask how soon the Safari application can have this update? Thanks.

I ended up upgrading my OS to Big Sur 11.3.1 from Catalina. Then the Safari web inspector tabs come back. Working combination: OS: Big Sur 11.3.1 Safari: 14.1.1 (15611.2.7.1.6) Xcode: 12.4 (12D4e)