DDL operations in MariaDB are known to not be crash-safe. The most unsafe is ALGORITHM=INPLACE, because the .frm file is replaced out of sync with the InnoDB transaction commit.

One thing that can be improved is that when the server is killed before the InnoDB transaction commit becomes durable, the intermediate table should be removable by executing a statement like

DROP TABLE `#mysql50##sql-abcd_1.frm`;

Currently, the intermediate table in the InnoDB internal data dictionary is not derived from the .frm file name, and such a DROP TABLE statement would leave orphan entries in the InnoDB internal data dictionary.