If, however, they don't seem to be a great fit for your needs, there are several other small Arduino boards you can use instead, including the Micro (18 by 48 mm), MKR Zero (25 x 61.5 mm) and MKR ...

Arduino has transitioned from the deprecated MbedOS to ZephyrOS, a modern open-source RTOS, to enhance real-time scheduling, multitasking, and overall embedded development capabilities.