There were plenty of those, including commercial ones.
It's pretty hard to find but ~25 years ago I was using Xi Graphics Accelerated-X which had 3D acceleration long before Xfree86.
Update: but yes I imagine it had some code from original MIT release.
For completely independent one you can have a look at WeirdX/WiredX, which was written in Java and even supported antialiasing and transparency for core protocol (something that Xfree86 people claimed to be impossible to implement).
Software solutions like Moonlight/Sunshine have been able to do that with near-zero latency for a long time and they are not even the first. Phones have chips capable of capturing 4K 120fps. Why is it so hard for KVM devices?
Can it help with the annoying macos bug that about half the time disconnecting and reconnecting external screen to my MacBook does not move windows back to external screen?
If you put a bomb in a box and attach a button with a note that the button is provided as-is and author disclaims any liability, then leave it in public place and someone presses it, do you think you will not be found liable?
Does takeout include any metadata not accessible via IMAP? Does it even include labels?