Problem:
E: The repository 'https://appcenter.software-univention.de/univention-repository/4.4/maintained/component oxseforucs_20191017183357/all/ Release' does not have a Release file.
E: The repository 'https://appcenter.software-univention.de/univention-repository/4.4/maintained/component oxseforucs_20191017183357/amd64/ Release' does not have a Release file.
Solution:
Add temporary [trusted=yes] to repository entry in sources list (remains only until the next ucr commit)
vim /etc/apt/sources.list.d/20_ucs-online-component.list
deb [trusted=yes] https://appcenter.software-univention.de/univention-repository/4.4/maintained/component/ oxseforucs_20191017183357/all/
deb [trusted=yes] https://appcenter.software-univention.de/univention-repository/4.4/maintained/component/ oxseforucs_20191017183357/amd64/
Note: using [trusted=yes] undermines the security chain of the Univention App Center repositories and allows undetected man-in-the-middle attacks. Use this snipped only as last resort in emergency cases.