https://mariadb.com/kb/en/innodb-recovery-modes/ contains the following paragraph:

To recover the tables, you can execute SELECTs to dump data, and DROP TABLE to remove corrupted tables.

The claim that DROP TABLE can be executed is only true for some modes. In reality, DROP TABLE (and any other manipulation) is disallowed starting from mode 4:

> DROP TABLE familipedia.page;
ERROR 1036 (HY000): Table 'page' is read only

Indeed, https://dev.mysql.com/doc/refman/8.0/en/forcing-innodb-recovery.html explains that "An innodb_force_recovery setting of 4 or greater places InnoDB in read-only mode." (although that seems to be inaccurate for MySQL, as the same page claims mode 4 supports DROP TABLE).

Note that it would be appreciated to make it clear if purging MariaDB data is the only solution when MariaDB fails to start in mode 3.