What electronics are inside the LEGO Powered Up hub? I'm curious what the internals of the new Powered Up hub look like? What components are inside?
The bulk of the space inside the Powered Up hub is consumed by the housing for the 6 AAA batteries. A small portion of the top of the hub contains the main printed circuit board. Here's how it looks removed from the hub:



And here's another shot showing the back:



The main chip is very similar to the one used in Boost. It uses an STM32F030 from ST Microelectronics. This includes a 32 bit ARM Cortex-M0 clocked at 48Mhz.

For Bluetooth Low Energy (BLE) communication, the Powered Up hub uses a CC2640 from Texas Instruments.

The largest chip on the underside of the board is an LB1836. I haven't done any testing on the traces, but that part is a dual-channel stepper motor driver and is placed near the output ports, so it is almost certainly used to drive the output current to servo motors. The front side includes a pair of 74HC2G125DP chips near the output ports. These are likely used select which CPU pin the output pin is connected to.