This Adafruit MCP23017 I2C GPIO Expander Breakout has 16 GPIO with a matching floor pad. It runs happily over 3V or 5V logic and power. Each GPIO can be output power up to 25mA, so LEDs are no problem. Or anyone can be inserted with an optional pull loop. There are two IRQ pins that are configurable for input to keep track of it. Therefore, no I2C bus queries is required. With 3 address pens, you can have up to 8 on a single bus for a total of 8 x 16 = 128 GPIO, all on an I2C bus.
Comes with two pin header so you can use it in a breadboard with some soldering. You can also connect freely wired buttons by connecting one side to the GPIO (set as input with pull-up) and the other side with a floor pad.
Adafruit has created solid Arduino and CircuitPython libraries with examples all ready for this chip. But even if you use another platform, the MCP23017 is so classic that you can probably find an example code.
To get you started quickly, they have a custom cut PCB in the STEMMA QT form factor, making it easy to connect. The STEMMA QT connectors on both sides are compatible with the SparkFun Qwiic I2C connectors. This allows you to create solderless connections between your development card and the MCP23017 or connect to a variety of other sensors and accessories via a compatible cable (not included).