Use TYPO3 users (from be_users table) for authentication in Dokuwiki. This uses the authpdo plugin (https://www.dokuwiki.org/plugin:authpdo)

local.php

<?php

/**
 * 
 * 
 * Currently only read only operations are implemented.
 * 
 * Reminder:
 * Configure password in configuration manager before switching authtype to `authpdo`.
 * Otherwise you locking yourself out of the system.
 */ 

$conf['authtype'] = 'authpdo';
$conf['passcrypt'] = 'bcrypt'; 

...

$conf['plugin']['authpdo']['dsn'] = 'mysql:host=127.0.0.1;dbname=typo3';
$conf['plugin']['authpdo']['user'] = 'typo3';
$conf['plugin']['authpdo']['pass'] = ''; // encrypted password. Best set this in configuration manager

$conf['plugin']['authpdo']['select-user'] = 'SELECT uid,
username AS user,
realName AS name,
password AS hash,
email AS mail
FROM be_users
WHERE username = :user
AND disable = 0
AND deleted = 0
AND (starttime < UNIX_TIMESTAMP()) 
AND (endtime=0 OR endtime > UNIX_TIMESTAMP())';

$conf['plugin']['authpdo']['select-user-groups'] = 'SELECT G.title AS `group` 
FROM be_groups AS G 
WHERE FIND_IN_SET(
        G.uid,
        (
        SELECT U.usergroup_cached_list
        FROM be_users AS U
        WHERE U.uid = :uid
        )
)
AND G.deleted = 0
AND G.hidden = 0
UNION
SELECT \'admin\' AS `group`
FROM be_users
WHERE uid = :uid AND admin=1';
$conf['plugin']['authpdo']['select-groups'] = 'SELECT uid AS gid, title AS group
FROM be_groups
AND deleted = 0
AND hidden = 0';

$conf['plugin']['authpdo']['list-users'] = 'SELECT DISTINCT username AS user
FROM be_users
WHERE username LIKE :user
AND realName LIKE :name
AND email LIKE :mail
AND disable = 0
AND deleted = 0
AND (starttime < UNIX_TIMESTAMP()) 
AND (endtime=0 OR endtime > UNIX_TIMESTAMP())
ORDER BY user
LIMIT :start,:limit';

$conf['plugin']['authpdo']['count-users'] = 'SELECT COUNT(DISTINCT username) AS count
FROM be_users
WHERE disable = 0
AND deleted = 0
AND (starttime < UNIX_TIMESTAMP()) 
AND (endtime=0 OR endtime > UNIX_TIMESTAMP())';