Thanks, I know this page and I know the difference between release and snapshot or factory and sysupgrade. In other threads even renaming of a sysupgrade-file was recommended. In theory I need a factory-file.
But that doesn't answer my question what I shall use, because of
(beware: no luci webinterface in snapshots). Some devices can not be downgraded to 18.06.1, but work ok with snapshot.
Maybe is someone here, who flashed a C7 v5 EU? At the end I would like to use LUCI.
And please tell me where do I have to put the file on the pc?