Sadly, after many hours troubleshooting this, the answer is that you cannot. Even with reduced motion and turning off as much animation as possible, there is a 1,000 millisecond input delay in switching workspaces on Mac. That is a fundamental limitation of the core operating system APIs.
If I remember correctly there is a command line option. I do it many year ago on my Mac, and I can switch space without any delay / animation
Edit :
You're right, there is some Fade transition between space, but it is not 1000 ms.
defaults write com.apple.dock expose-animation-duration -int 1; killall Dock