I was able to build CEmu 1.3dev version with sailfish sdk 3.0.3.9.
It builds without any problems.
A big problem were the graphic arrangements so I tried to disable some dockwidgets. But in the end it could be really that the key was to get a good config file.
So I will attach my config file. You need to change the rom_path= and the scale=.
The rom path will point to your rom file. The scale value is the scaling of the calculator screen. I will give you the optimal values for the specific resolution.

540x960 scale=94
720x1280 scale=124
1080x1520 scale=194

In principle it could be possible, with a different configuration, that the keypad isn't docked which results in bigger size, in doing so will make the keypad get centered in which the screen is on the left side.

The cemu_config.ini, after removing txt extention, copy to /home/nemo/.config/cemu-dev/CEmu

This is an experimental version. You will need to dump your rom from the calculator.

CEmu-1.3.0-1.armv7hl.rpm