I recently did a release upgrade of an Ubuntu server (22.04 LTS Jammy to 24.04 LTS Noble) in one of the cloud providers we have.
I followed the 3. Upgrading in-place guide.
This went overall well, but the website did not load. It seems that during the release upgrade, the OMD config was removed from /etc/apache2/config-enabled/
Perhaps a small addition on the documentation could be (troubleshooting) to check that zzz_omd is enabled in apache2, and how to do it:
a2enconf zzz_omd