Actually, you need these three repos according to the official doc.
https://en.opensuse.org/SDB:System_upgrade_to_Leap_15.4#1._Check_if_the_3_update_repositories_already_exist_and_are_enabled_and_update_before_upgrading.

From: Robert Munteanu <rombert@apache.org>
Sent: Monday, June 13, 2022 11:46:47 PM
To: Guillaume Gardet <Guillaume.Gardet@arm.com>; arm@lists.opensuse.org <arm@lists.opensuse.org>
Cc: nd <nd@arm.com>
Subject: Re: Leap 15.4 aarch64 repo?
 
On Mon, 2022-06-13 at 15:13 +0000, Guillaume Gardet wrote:
>
>
> > -----Original Message-----
> > From: Robert Munteanu <rombert@apache.org>
> > Sent: 13 June 2022 16:46
> > To: arm@lists.opensuse.org
> > Subject: Leap 15.4 aarch64 repo?
> >
> > Hi,
> >
> > I tried to update one of my RPi4 boxes to Leap 15.4 today, but it
> > seems there is
> > no 'repo-oss' published at
> > https://download.opensuse.org/ports/aarch64/distribution/leap/15.4/
> >  .
> >
> > Am I looking in the right place or is there something else going
> > on?
>
> You need to look at
> https://download.opensuse.org/distribution/leap/15.4/repo/oss/
> Basically, just drop ports/aarch64/ from your URLs.

That works, thanks Guillaume!

Robert