2 WordPress sites in 2 sibling folders on one domain

install a normal wordpress like it was to install only one

in this case in /var/www/vhosts/domain.com

Website 1:

Domain name: domain.com
Physical folder: /var/www/vhosts/domain.com
URL: https://domain.com/
CMS: WordPress One (with database one)

now /var/www/vhosts/domain.com has all wordpress files and folders

in this directory /var/www/vhosts/domain.com create a new folder called test

now install a new wordpress in /var/www/vhosts/domain.com/test

Website 2:

Domain name: domain.com
Physical folder: /var/www/vhosts/domain.com/test
URL: https://domain.com/test
CMS: WordPress Two (with database two)

and this is how you get two wordpress sites with two different databases in the same domain. basically you create a folder inside that has another wordpress , the main wordpress never goes there because doesnt know that exists. and can be access by directly writting the url with the folder name. this is good for developing a second version of the website, or to have two websites in one domain also.