I am new to Teensy, and started with a 3.2 board, thinking it should offer similar capabilities of STM32 Nucleo-L476 as they are both facilitating the Cortex M4.
The divide however seems to be large?

On STM32 I am used to using the HAL library, where it is easy to connect to peripherals and also getting callbacks that will run in independent threads.
Unfortunately I am not able to find out how to do that with the Teensy 3.2, so if someone could please tell me to find such info?

In short, I have a main loop that continuously makes decisions dependent on the values from various sensors (temperature, humidity, Hall, light, etc.), and adjust various timer's PWM duty cycles.
Those sensors may be read during the main loop, but also on external interrupts that calls independent functions.
Then, I use a UART Rx/Tx to access a running system, and this is also interrupt driven executing in its own threads.

As all Nucleo boards I have seen are rather large in physical size, I found the Teensy 3.2, which is impressively compact in size, and I thought it would be rather similar to the Nucleo to program.

Multi-thread wise it seems not so?
Can anyone please tell me where to look?