Hi @tthenrie and thanks for your efforts to enliven this forum. Unfortunately, I am just an ordinary home computer user, a refugee from MS Windows with no programming skills nor Unix (BSD, Linux) experience at all.
Fortunately, all the installed apps, including GIMP, Inkscape, Feh, Qpdfvew, and Viewnior are working correctly for me, so I am a happy NomadBSD user on my thirteen years old Acer Aspire 7738G laptop.
Just one my hint might come in handy for you. Looking for alternatives to IrfanView (for MS Windows only), I have installed GraphicsMagick (it is also installed as a dependency for Inkscape). GM is a CLI app for programmers mainly, yet also has a minimal GUI that I have adapted by adding a command ‘gm display’ to the context menu “Open using…” for JPEG, PNG, SVG, ico, and other graphic files. GraphicsMagick is available from Octopkg.