Step one would be opening a bug report at https://gitlab.gnome.org/GNOME/dia/-/issues/new foursqaured button?
Well there has never been an official release for macOS as such, so whatevers on dia-installer.de is the latest The next release will have an official macOS version
That page (and this one...) were maintained by a third party who is no longer around For help getting existing releases to work on Catalina see https://gitlab.gnome.org/GNOME/dia/-/issues/472 Hope that helps :-)
Block Dia from saving backup copies of files.
Unfortunately there is no option for this, but it might be worth adding
Is the project abandoned?
This sourceforge project was never the official home of Dia and is dead Dia however remains maintained where it has always lived at GNOME, a new release is planned in a year or so
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