I am able to connect my Samsung S2 tablet to spacedesk. But there are only 2 resolution options to choose from: 2560×1600 (native) or 1024×768. I want to have a lower resolution, but the second one is 4:3. The screen looks horizontally stretched. Is it possible to have a 1280×800 resolution?
You can set a different custom resolution in the Resolution setting of the viewer app
either by choosing from drop-down menu pre-defined resolutions or you can manually enter it.