TiDB is a MySQL-compatible database, but it does not support all features in MySQL (or MariaDB). Is there some prominent user of WordPress using TiDB as the database? Is TiDB known to be compatible enough to be used with WordPress?
There is no mention of TiDB at Stats – WordPress.org nor at Requirements – WordPress.org, and various websites/blogs seem like one-off tests.
You can check the document Connect to TiDB Cloud Serverless with WordPress
A known issue is that TiDB does not support the SQL_CALC_FOUND_ROWS function, and MySQL is also planning to remove this function in a future release, suggesting that COUNT(*) be used instead.
You can resolve this issue by install a Wordpress TiDB plugin, and find the detail explanation in the README.md of the plugin repository.
Thanks!