Can I use PostgreSQL when installing erpnext12 ?

[lapphan]

I am afraid the answer is can not at this time.

Support for PostgreSQL?

Frappe Framework is ready for Postgres but ERPNext is not. There are 1300 queries that might need refactoring as of July 2019. If there is anyone willing to sponsor and use this in production, this is a project we can definitely invest time and effort.