Move data with schema change between MariaDB servers
Write a SELECT statement that JOIN the two tables together.  Specify exactly the target columns desired (most coming from one table, one from the other table).
Then do


Something like

INSERT INTO new (a,b,c,d)
    SELECT x.a, x.b, x.c, y.d
        FROM x
        JOIN y ON ...


For reading from one server and writing to another, see FEDERATEDx.