MSSQL implements geometry via the Common Language Runtime (CLR). This implementation doesn’t allow you to call these function across linked servers. The solution is to create a view and  convert the geometry into x,y values (or lat/long for geography).

Then convert your data back into geometry when exposing the data in a view on the destination.

Example:

SELECT x
,y
,GEOMETRY::STPointFromText
('POINT(' + CONVERT(VARCHAR(30), x)
+ ' ' + CONVERT(VARCHAR(30), y)
+ ')', 2927) AS shapegeometry