Hello,
Last time Dia got an official tag, it was in 2011 (0.97.2). For some reason, an untagged 0.97.3 Dia release has been pushed to the Gnome download center ( Index of /sources/dia/0.97/ ) in 2014. Since then, a lot of useful patches/fixes have been merged into the main tree but none of the new contributions received the honor to appear in a new release yet.
The problem is that most mainstream distributions do package the latest release and not the latest HEAD, so they are stuck with a 12 years old -slightly buggy- version. Only rolling distributions such as ArchLinux or Gentoo embed the latest (stable/fixed) version of Dia.
As an example, Dia has issues generating SVGs with PNGs inside, this has been fixed upstream for quite some time. One solution would be to ask each and every package maintainer of every distribution to cherry-pick a number of patches, but it would be much cleaner for the whole ecosystem if Dia official version could be bumped.
Thanks a lot for considering this request,
Miquèl