@Caefix Here's a test build for ixus230_elph310hs-100e. If you can, please run ndtest, and test synced remote and dark frame subtraction (DFS) control.
To test synced remote:
Without USB connected, go to CHDK Settings->Remote parameters and set
* Enable remote
* Switch Type: One push
* Control mode: Normal set
* Enable remote sync
You can test by plugging into a PC or powered hub. When you plug in, the camera should focus and the screen will probably go black. When you unplug, it should shoot. If you wait more than 10s without unplugging, it will shoot anyway.
To test DFS
Set shooting mode to long shutter, and shutter to 5s. With CHDK Enhanced Photo Operation -> Dark Frame Subtraction in ON or Auto, a shot should take 10s instead of 5, with the camera probably showing BUSY for the second 5s. With DFS OFF, it should take only 5s.
If you use a 1s exposure, it should take 2s with 1s of BUSY with DFS, and take only 1s with it off.