You have an installation of MySQL 8 on Oracle Linux.

In MySQL 8.0, the default storage engine for temporary tables is InnoDB. The InnoDB temporary tablespace is located in the data directory and is used for all temporary tables. The tmpdir variable is used for other temporary files, such as binary log files and slow query log files1. The tmp_table_size variable only affects the maximum size of internal in-memory temporary tables, not disk-based temporary tables2. The TABLESPACE clause for CREATE TEMPORARY TABLE is deprecated and does not affect the location of the temporary tablespace3. References:

1: https://dev.mysql.com/doc/refman/8.0/en/internal-temporary-tables.html

2: https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_tmp_table_size

3: https://dev.mysql.com/doc/refman/8.0/en/create-temporary-table.html