STM32 microcontroller, such as any nucleo board
Shield: if you are not looking for the direct nucleo hat you may try the PowerShield-D (the new discrete component shield).
Encoder: This is a rather complex topic. Generally SPI magnetic absolute encoder such as AS5047P would work, however this really depends on the motor and use case.
If you are looking for a fully integrated board then you need to be a lot more specific about you use cases. I’m not sure what