BUG #16564: Can't start the service postgresql@11-main.service

The following bug has been logged on the website:

Bug reference: 16564
Logged by: Stemy
Email address: stemy(at)stemy(dot)me
PostgreSQL version: 11.2
Operating system: Debian
Description:

Hello,

I can't use any server app that requires a postgresql database.

I can't even start the service. It is marked as "inactive (dead)", and if i
execute "systemctl start postgresql(at)11-main(dot)service", it returns me this:
"Assertion failed on job for postgresql(at)11-main(dot)service(dot)".

Here's what a "systemctl status" give:

● postgresql(at)11-main(dot)service - PostgreSQL Cluster 11-main
Loaded: loaded (/lib/systemd/system/postgresql(at)(dot)service; enabled; vendor
preset: enabled)
Active: inactive (dead)
Assert: start assertion failed at Thu 2020-07-30 19:13:54 CEST; 1h 21min
ago
AssertPathExists=/etc/postgresql/11/main/postgresql.conf was not
met

So what have i to do to "resurrect" it ?

Thanks.