Looking at a vanilla "DGIndex.exe", it seems like it contains an
empty manifest.
You may wish to replace that with the following content, e.g. by using
Resource Hacker, in order to enable UTF-8 support:
(requires Windows 10, Version 1903 or later!)
Code:
<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
<assemblyIdentity type="win32" name="avisynth.dgindex" version="1.0.0.0"/>
<application xmlns="urn:schemas-microsoft-com:asm.v3">
<windowsSettings>
<longPathAware xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">true</longPathAware>
<activeCodePage xmlns="http://schemas.microsoft.com/SMI/2019/WindowsSettings">UTF-8</activeCodePage>
</windowsSettings>
</application>
</assembly>
In my test this worked fine. Even though not all characters may display correctly in the GUI, the input file was opened and the output file was generated without problem:
https://i.imgur.com/n3DokZn.png