To enable the Gboard split keyboard you need to go to the Settings> Preferences>Layout is enabled. After that Gboard keyboard places split with an equal number of keys on the left and right when the Split layout includes duplicated keys option is enabled. Now, the Gboard Split keyboard feature comes to Android tablets.
When this feature is turned on the user can switch between the Standard and Split keyboard options from a toolbar tile. This feature now user use on the Galaxy Tab S8 with Gboard beta version 12.9.21.
Google launched this feature last year for foldable like Galaxy Fold and Surface Duo.
Finally, this feature is now available on some tablets, and when the Pixel Tablet will release then users can use it on that also.