When modifying packages derived from Debian, per [1] Ubuntu developers use [2] to set "Ubuntu Developers <email address hidden>" as the maintainer.

This group only owns that address so people can find a trace when e.g. coming here from a package page in launchpad which will refer to the uploader.
And in the case of such a package that set <email address hidden> that will be here.

This is all pretty generic, you most likely want to contact the last uploader
or if known even better the owning team - if it is a package in main the mapping [3] might help to find that.
Or to be fair - even better - file a bug against the package, most teams have established a pretty decent
regular triage.

[1]: https://wiki.ubuntu.com/DebianMaintainerField
[2]: https://manpages.ubuntu.com/manpages/noble/man1/update-maintainer.1.html
[3]: http://reqorts.qa.ubuntu.com/m-r-package-team-mapping.html