Am also victim of the above said issue,
Workarounds:
Turn Off Assistive Touch & Perform Touch Gestures:
Magic Keyboard will work perfectly without any lag, and external mouse (am using logitech mx master) will work its basic functions,
2. Turn On Assistive Touch & Perform Touch Gestures:
Magic Keyboard andExternal mouse will perfectly work, but you will have big stupid circle pointer.
Awaiting an update to fix this.
Cheers
jobythomaz
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