It seems that the xposed installer is not anymore updated.
Im not sure but as far I understood the issue on their github the Problem could be solved.
The update for Xposed Installer is automatic based on github tags. They should fix the tag there.
Xposed Installer does not comply with the inclusion policy. See Xposed Installer (#331) · Issues · F-Droid / Requests For Packaging · GitLab
In any point in time, will the Xposed team fix this? I’m on version 89 and still getting this nagging message upon every app update.