TYPO3 Core

In TYPO3 v12 the field config MM_hasUidField is required to be
set in conjuction with multiple = true for following TCA types

• select
• group
• inline
• category

and only if defined on the local side for a MM relation, which
means the one without the MM_opposite_field configuration.

Granted, the documentation only mention TCA type group for
that option [1], which is literally not the complete list.
That means the documentation needs to be corrected if I'm
correct that this options is required.

NOTE: This already changed with TYPO3 v13 where MM_hasUidField has
been removed, with Issue #101554 [2] and also related to #101425
for issues with MySQL Galera Clusters.

That means, your TCA configuration should be:

'test' => [
    'exclude' => 1,
    'l10n_mode' => 'exclude',
    'label' => 'test',
    'config' => [
        'type' => 'select',
        'renderType' => 'selectMultipleSideBySide',
        'foreign_table' => 'tx_tea_domain_model_coffee',
        'foreign_table_where' => 'AND tx_tea_domain_model_coffee.sys_language_uid IN (-1,0) Order by title ASC',
        'MM' => 'tx_tea_tea_coffee_mm',        
        'size' => 10,
        'autoSizeMax' => 30,
        'maxitems' => 9999,
        'multiple' => 1,
        'MM_hasUidField' => true, // <--- THIS ONE should be required because of `multiple: 1`
    ],
],

[1] https://docs.typo3.org/m/typo3/reference-tca/12.4/en-us/ColumnsConfig/Type/Group/Properties/Mm.html#confval-mm-hasuidfield-type-group
[2] Issue #101554 https://review.typo3.org/c/Packages/TYPO3.CMS/+/80434

There is an Issue in the GitHub docs tracker for this: https://github.com/TYPO3-Documentation/TYPO3CMS-Reference-TCA/issues/1054

I'm closing the issue for this for now, and it will be addressed in docs. Thanks for the good writeup.

(Also closing because of lacking follow-up feedback)