ST_Touches(g1, g2)

Two geometries spatially touch if their interiors do not intersect, but
the boundary of one of the geometries intersects either the boundary or
the interior of the other.

This function returns 1 or 0 to indicate whether g1 spatially touches
g2.

ST_Touches() handles its arguments as described in the introduction to
this section except that the return value is NULL for the additional
condition that both geometries are of dimension 0 (Point or
MultiPoint).

URL: https://dev.mysql.com/doc/refman/8.0/en/spatial-relation-functions-object-shapes.html

