ppa/ubuntu lunar release not found

[mstumpel]

Hi,
I am trying to update my omv (6.9.6-1 (Shaitan) running on xu4. The update is cancelled with the error :

E: The repository 'http://ppa.launchpad.net/hardkernel/ppa/ubuntu lunar Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.

How can I solve this? is there a way to override or to get a lunar release file or something else

[tobetter]

I am wondering what makes you to add the repository Ubuntu 23.04 (Lunar) over OMV that is based on Debian 11.
Do you have any specific package to be updated?

Two problems here, IMO, 1) There is no package update for Lunar and 2) The package would not compatible with OMV6.

[mstumpel]

I get this error when I execute omv-upgrade. Probably this script is not correct