In "Split alpha" -> "Save merged", the file type "all supported formats" is selected by default, and ".exr" is the first extension in the list. This means if the user doesn't enter a file extension, exr is used by default. Due to EXR's use of premultiplied alpha, it may mangle the colour data of transparent pixels. It seems to me if the image is 8-bit per channel then having PNG as default would be the better choice...
I've removed the all suported format entry now. See https://invent.kde.org/graphics/krita/commit/362feb5d0cc25a7d16e5723a0081da85125b0514
Reopening since the commit has been reverted.
Git commit 8141535c0450ec62d24923973a6b634775ccb4e2 by Halla Rempt. Committed on 09/09/2021 at 13:20. Pushed by rempt into branch 'master'. Make sure that *.kra is the first item in "All Supported" Related: bug 437831 M +5 -19 libs/widgetutils/KoFileDialog.cpp https://invent.kde.org/graphics/krita/commit/8141535c0450ec62d24923973a6b634775ccb4e2
Git commit 4c6899cbeff9c64f5c513d7e234f565e75f1ad70 by Halla Rempt. Committed on 09/09/2021 at 13:21. Pushed by rempt into branch 'krita/5.0'. Make sure that *.kra is the first item in "All Supported" Related: bug 437831 (cherry picked from commit 8141535c0450ec62d24923973a6b634775ccb4e2) M +5 -19 libs/widgetutils/KoFileDialog.cpp https://invent.kde.org/graphics/krita/commit/4c6899cbeff9c64f5c513d7e234f565e75f1ad70