Can't unlock bootloader. Suggestions?
The download tool for worldwide firmware is available here. https://www.asus.com/us/Phone/ZenFone-6-ZS630KL/HelpDesk_Download/
If you are not on WW firmware, please go to your regional ASUS support website for the correct download.
You don't need to do that for downgrade.
Have you found any way..to downgrade to android 9
Did you downgrade to android 9?