Please see but 135513 concerning the inoperabliity of Dynamic Data Exchange. It appears that the bug report has not been reviewed. I attached a zip file with linked Calc and Writer files that worked in LO6 versions, but do not work in LO7. I have also made simpler linked files in LO7 and still no updating in Writer when data is changed in the linked Calc file.
I submitted bug 135513 stating that DDE is inoperable in LO7. Is this function being abandoned or will it be made operational and continue to be part of the application?
You created a bug report, so no need to inform users of LibreOffice about this fact. This site is not a communication path to developers and reviews are done on a voluntary basis based on availability of developer resources, interests, severity and whatever other factors … This is a non-commercial free and open source project.
Regarding the question: LibreOffice 7.0: Release Notes does not contain any information regarding changes in DDE functionality.
Update: There is another bug report [#tdf135676](https://bugs.documentfoundation.org/show_bug.cgi?id=135676) which might be a duplicate and has been reviewed. May be you could leave a message there.