SharePoint Server 2019 September 2020 Public Update Bug12 Sep 2020 | SharePoint 2019
For the SharePoint Server 2019 September 2020 language-specific update KB4484504, there is an issue with non-English languages and Modern sites. On modern sites, the Site Contents and Command Bar in Lists/Libraries is not rendering. A case was opened and the bug was confirmed.
My recommendation for non-English farms is to hold off on the September 2020 PUs for SharePoint Server 2019 at this time.