Which command did you run to add the repo .list file?
In addition to changes to how the GPG key is downloaded and installed, the line added to openhab.list is changed to use that key.
Make sure the line looks like:
deb [signed-by=/usr/share/keyrings/openhab.gpg] https://openhab.jfrog.io/artifactory/openhab-linuxpkg stable main
in /etc/apt/sources.list.d/openhab.list
Notice the “signed-by” part. That’s new too.