MariaDB [test]> create table tpa(id int, c1 varchar(10)) partition by range(id) (partition p1 values less than (10), partition p2 values less than (1000));

Query OK, 0 rows affected (0,310 sec)

MariaDB [test]> ALTER TABLE tpa MODIFY COLUMN c1 VARCHAR(30), LOCK=NONE, ALGORITHM=INSTANT;

ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Cannot change column type. Try ALGORITHM=COPY

MariaDB [test]> ALTER TABLE tpa remove partitioning;                            

Query OK, 0 rows affected (0,757 sec)

Records: 0  Duplicates: 0  Warnings: 0

MariaDB [test]> ALTER TABLE tpa MODIFY COLUMN c1 VARCHAR(30), LOCK=NONE, ALGORITHM=INSTANT;

Query OK, 0 rows affected (0,076 sec)

Records: 0  Duplicates: 0  Warnings: 0

MariaDB [test]> select version();

+-----------------+

| version()       |

+-----------------+

| 10.4.12-MariaDB |

+-----------------+

1 row in set (0,000 sec)