There's 6 extra pins over the promicro which is a footprint a lot of boards target. https://beta.docs.qmk.fm/developing-qmk/c-development/compatible_microcontr

There's 6 extra pins over the promicro which is a footprint a lot of boards target. https://beta.docs.qmk.fm/developing-qmk/c-development/compatible_microcontrollers https://beta.docs.qmk.fm/developing-qmk/c-development/compat... list of things QMK supports. There are a few bluetooth keyboard controllers that already fit the bluetooth controller niche and are pin compatible (nice!nano). This having a microusb port would make it less appealing as well. Personally I'm more interested in the RP2040 Pro Micro variant. It uses KMK, works with circuit python and can have its keymap changed by editing a file on it rather than reflashing or being limited by Via/Vial.