# choose profile to use (`in-portal.full` or `in-portal.community`)
# checkout In-Portal 5.2.x using chosen profile
# checkout In-Portal 5.3.x via `in-portal` module and then run `php /tools/configure_profile.php profile_name` script using chosen profile
# install In-Portal 5.2.x
# copy over `/system/config.php` file from In-Portal 5.2.x installation to In-Portal 5.3.x installation (fix `WebsitePath` setting if needed)
# open `/core/install.php` in the In-Portal 5.3.x installation
# run upgrade till `Module Select` step
# execute `Module Select` step
# confirm, that no error about wrong SQL was displayed
# discard any other error you might see