After updating from Firefox 97 to 98, i no longer can use my workaround in about:config:
widget.non-native-theme.enabled = false
widget.content.gtk-theme-override = Windows-7-2.1
widget.non-native-theme.scrollbar.size = 24
Windows-7-2.1 is my GTK Theme.
Looks like Mozilla trying to forced me to use the Breeze Scrollbar from KDE in Firefox 
https://www.reddit.com/r/firefox/comments/tae5ri/how_to_reenable_native_widgets_in_firefox_980/
Anyone know a solution? I really dislike the Breeze Scrollbar 