Magento 2 Setup di Compile Problem

Search for the missing class in your magento2 code, you can do via linux cli:

find /path/to/magento2-root -type f -iname '*.php' -print0 | xargs -0 grep -nw -e 'Magento\\Email\\Model\\Source\\Variables'

and comment any line calling this class (that was removed from magento2.3)

UPDATE

You can also change this class in Magento 2.3 for Magento\Variable\Model\Source\Variables

I just replaced the class Magento\Email\Model\Source\Variables with Magento\Variable\Model\Source\Variables.

Class Bss\HtmlSiteMap\Model\Filter

public function __construct(
    ...  
    \Magento\Email\Model\Source\Variables $configVariables,
    ...
)

replace

public function __construct(
    ...  
    \Magento\Variable\Model\Source\Variables $configVariables,
    ...
)

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