I’m sounding a little like a stuck record with this, but if your mobile is also due an upgrade, have you considered a Huawei P9? The second, B+W specific camera is excellent in low light. I have been able to capture images with it which are as sharp as a colour photo in the daylight.
The automatic exposures are really nice, with the Leice software doing all the calcs to give you a great picture most of the time. There is also a full manual mode, exposures of up to 30 seconds are possible as well as ISO from 50 to 3200, and Shutter from 1/4000 to 30seconds. There is also DNG/RAW output and the aforemantioned pair of separate cameras.
Here’s a few examples, not the very best that is possible, but just to show you. All have been downsized and resaved, so there’s extra jpeg compression in there.
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30 seconds, just rested the phone facing up. The case settled, hence the star trails.
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Can also do fake bokeh using the depth map from the cameras.
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Both indoors in very dim room. Hand held.
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Took this after the sun had set, really dark. Hardly broke my stride, still sharp.
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This is actually taken with a Moto G v1, which has a notoriously poor camera. Just to show that fiddling with the settings can get you a fair way with even a crap camera.