I use Inkscape and want to export a PNG image (of my SVG file) with dimensions 1080 px by 1920 px. However the DPI is always set to 90 and if changed, the dimensions change with it. Is it possible to have a higher DPI with the same dimensions?
1) If you want a file 1920×1080 px, the ppi is TOTALLY irrelevant, because you want it for an electronic medium.
2) In the case of the export focus on the pixel size. Yes, on the moment of the export, the ppi and the dimensions are intertwined but after that, you can change that in gimp or another aplication like IrfanView.
3) You could try to change the dimensions before exporting, but there is no point in doing so.