The SparkFun Qwiic 12 Bit ADC can provide four channels of I2C controlled ADC input to your project. These channels can be used as single-ended inputs, or in pairs for differential inputs. What makes this even more powerful is that it has a programmable gain amplifier that lets you "zoom in" on a very small change in analog voltage (but will still effect your input range and resolution).
The ADS1015 uses its own internal voltage reference for measurements, but a ground and 3.3V reference are also available on the pin outs for users. This ADC board includes screw pin terminals on the four channels of input, allowing for solderless connection to voltage sources.
More information is available on the website of Sparkfun.