Try to set the resolution to 2560x1080 (21:9). If still everything is to small, try to set a bigger font.
For the background you might have to resize (in percentage) the picture, and keep the relation on (21:9).
I guess you want to make a smaller resolution to get it more readable ?!
I am also looking for a similar solution to this problem, just on the other dimension. I have 1920x1200 displays that for purposes with OBS recording/streaming I would like to be able to set to 1920x1080. The inability to do so results in either having scaling artifacts and pillarboxing in OBS, or having to manually size application to fit the canvas exactly (which doesn’t work for fullscreen applications).
It would be ideal if there was a way maintain 1:1 scaling when changing display resolutions rather than stretching to fit the screen, though I don’t know if this is a hardware limitation with my displays or a GNOME issue.