Gramps Web and the Gramps Web Sync are not yet 6.0 ready. (@DavidMStraub has not projected a release date.)
So, new Gramps Web users having to install a desktop app will need easy access to the legacy 5.2.4 downloads. (As will users who uninstalled prior to upgrading to 6.0 before discovering the incompatibility. Those users will also need to backup to XML to downgrade from schema 21.)
What is the easiest way for users to have access to Gramps for Desktops 5.2.4 installers across all the platforms?
This is likely to be an recurring issue since Gramps Web will likely lag behind new major releases.