We got reports at the uyuni-users that some packages, namely "spacewalk- backend-*" and "python3-psycopg2" were not being updated.
The reason is that we need a temporary vendor change for "python3-psycopg2" as we provide an updated version for the repository syncing performance improvements, that should arrive to openSUSE Leap 15.1 in the following weeks.
Sadly this information was missing at the original release notes, so we apologize for that.
To fix it, after running "zypper update" you will need force the vendor change with
zypper in python3-psycopg2-2.8.4-2.1.uyuni.x86_64
Then update again again, so the spacewalk-backend subpackages are updated:
If you already updated to 2020.05, just stop the services with spacewalk- service, run the two steps above, and then start the services again.
All other packages such as "lucene" can be ignored.
The release notes at the website  are already updated (because of the release procedure, we can update the RPM packages for Stable), and we did an announcement at the website. A tweet at Twitter will follow soon.
Thank you very much to Philippe Bidault and Cristian Gherman for reporting the issue and helping testing the fix.