Have you tried to install Mailchimp on Magento 2.3 and got this message in SSH ” mailchimp error PHP Fatal error: Allowed memory size of 1610612736 bytes exhausted (tried to allocate 67108864 bytes) in phar:///usr/bin/composer/src/Composer/DependencyResolver/Solver.php on line 223 ”

Follow this procedure and you should be able to install it without issue

Access your SSH console.

Navigate to the root of your installation.

run the following commands

php -d memory_limit=4096M /usr/bin/composer require mailchimp/mc-magento2:102.3.38

Ignore the yellow messages.

php bin/magento cache:flush

php bin/magento module:enable Ebizmarts_MailChimp

php bin/magento setup:upgrade

php bin/magento cache:flush

php bin/magento setup:di:compile

php bin/magento cache:flush

php bin/magento setup:static-content:deploy -f

php bin/magento cache:flush

Thats it.