My localhost environment is running postgreSQL with phpBB 3.1.10 and 3.2.0, there are no issues. This problem is isolated to quickinstall.
The pgsql dbms is either not supported, or the php extension for it could not be loaded.
BACKTRACE
FILE: [ROOT]/includes/qi_functions.php
LINE: 533
CALL: trigger_error()
FILE: [ROOT]/modules/qi_manage.php
LINE: 75
CALL: db_connect()
FILE: [ROOT]/includes/functions_module.php
LINE: 52
CALL: qi_manage->__construct()
FILE: [ROOT]/index.php
LINE: 296
CALL: module_handler->load()
PostgreSQL 9.5.6 on x86_64-redhat-linux-gnu, compiled by gcc (GCC) 6.3.1 20161221 (Red Hat 6.3.1-1), 64-bit
PHP Version 5.6.29