Symptoms:

Magento website throws the error containing:

Processed schema file: public_html/vendor/magento/module-elasticsearch/etc/esconfig.xsd
complex type 'mixedDataType': The content model is not determinist.

That may happen after WHM updated EA provided library: ea-libxml2

Magento recommends to downgrade that library which is not good solution.

Temporary fix can be applied instead

Remove the line:

<xs:element type="xs:string" name="default" minOccurs="1" maxOccurs="1" />

in file: /home/<user>/public_html/vendor/magento/module-elasticsearch/etc/esconfig.xsd

That fix works immediately.

Issue discussion on Git: https://github.com/magento/magento2/issues/38254