[bitnami/postgresql-ha 11.9.7] psql version mismatch with server version

[juniperlorelei12]

Name and Version

bitnami/postgresql-ha 11.9.7

What architecture are you using?

amd64

What steps will reproduce the bug?

1. Checkout postgresql-ha version 11.9.7 chart
2. Install the chart
3. Wait for pods to spin up
4. Exec into pgpool pod using kubectl exec -it <pgpool-pod-name> -- psql --host <app-name>-postgresql-ha-pgpool -U postgres -d postgres
5. Immediately be greeted by the warning:

psql (14.9, server 15.4)
WARNING: psql major version 14, server major version 15.
         Some psql features might not work.

6. type \z
7. Get the following error:

ERROR:  operator is not unique: unknown || "char"
LINE 16:            E' (' || polcmd || E'):'
                          ^
HINT:  Could not choose a best candidate operator. You might need to add explicit type casts.

Are you using any custom parameters or values?

The only change I made to values.yaml is more than likely irrelevant to the issue. Regardless, I made lines 1070-1072 the following:

  customUsers:
    usernames: "jiradbuser"
    passwords: "jiradbpassword"

because my client wants to use Postgres with Jira. This is also why I'm using a specific version of the chart. As far as I can tell, 11.9.7 was the last version of these Helm charts to use Postgres 15, which is a prerequisite for Jira.

What is the expected behavior?

I expect not to be greeted by a warning that explicitly says "some features might not work" on a fresh install.
I also expect to see a list of all user permissions in response to \z, instead of an error.

What do you see instead?

I'll repeat myself, as required.
When logging into Postgres, I see the warning:

psql (14.9, server 15.4)
WARNING: psql major version 14, server major version 15.
         Some psql features might not work

When I run the command \z, I see the following error INSTEAD of a list of user permissions:

ERROR:  operator is not unique: unknown || "char"
LINE 16:            E' (' || polcmd || E'):'
                          ^
HINT:  Could not choose a best candidate operator. You might need to add explicit type casts.

I'm not certain, but I suspect that this issue is causing me cascading issues with my Jira setup.
As mentioned, I'm trying to stand up Postgres to connect to Jira, and after the "Database setup" page during the Jira setup wizard, I start to get HTTP 500 errors

Additional information

I've tried researching this issue and all of the solutions say to either uninstall and reinstall Postgres, or just point to a different version of psql that's already installed. Obviously, I do not control the version of psql that comes with this helm chart
I've also tried downgrading Postgresql to version 14, which does get rid of the warning. However, this is not a solution because Jira doesn't support Postgresql version 14, only 15.

How do I upgrade psql to version 15? (If that is the best solution, that is)