You would need to contact Gboard support for issues with there app.
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I searched the web and found several similar topics for other keyboard apps as well, my guess is that Samsung has a "private" fix for its own keyboard which does not conform the standard key mapping for RTL brackets (')', '>','},']' and '(', '<', '{','[') and that is why all the other keyboard apps fails, unless they will implement also a non-standard mapping just for Samsung devices.
