For V5, yes, still the good MCP23017, although we moved to the QFN-28 package. The price is higher than 2 years ago, but it’s almost the same with every chip.
The V5 control board looks like this:
we put the electronics for every key (RGB LED + 2 x 402 ceramic caps) under the silicone pad:
Note the JST-XH connector labeled as EXT-1. It’s for hardware extensions like CV/Gate module, etc. The pin-out is:
1. GND
2. INT7 (GPIO pin)
3. INT6 (GPIO pin)
4. SCL
5. SDA
6. 5V
Enjoy!