It should list other 16:9 resolutions... You can try manually changing the resolutions to 2048x1152, or something (see below).
Alternately, if you temporarily lower your desktop resolution, it may get lower 16:9 resolutions to show up in the game options (at least the new desktop resolution), after which you can restore your original desktop resolution.
Please email supportdos@larian.com, with a description of the problem and the report.zip file generated by the
D:OS support tool. The zip will include your saves (which aren't really necessary in this case, so you could delete them to reduce the file size) as well as the game settings and system specs, so would hopefully help them improve the resolution detection / filtering, as well as the bug with the black icons at max resolution.
You can edit the graphicSettings.lsx file (in the '..\Documents\Larian Studios\Divinity Original Sin' folder) in Wordpad, or other text editor, to manually change the resolution. Search for the section:
</node>
<node id="ConfigEntry">
<attribute id="MapKey" value="
ScreenHeight" type="22" />
<attribute id="Type" value="0" type="5" />
<attribute id="Value" value="
1600" type="4" />
</node>
<node id="ConfigEntry">
<attribute id="MapKey" value="
ScreenWidth" type="22" />
<attribute id="Type" value="0" type="5" />
<attribute id="Value" value="
2560" type="4" />
</node>