There are lot of tutorials about connecting the ESP32 to a cloud service, but I planned to connect these boards using MicroPython directly to the cloud. That means, I didn't want to use a hardware or software bridge. I wanted to use the Google IoT Core, but MicroPython doesn't support JSON Web Token (JWT), which is needed for the device authentication. I tried to write the library myself, but it didn't work, because of the needed dependencies and the small memory available on the ESP modules. But, I found Zerynth. Zerynth supports JWT and using it, it is possible to connect the ESP32 directly to the Google IoT Core. The company Zerynth defined its product as "the middleware for IoT and Industry 4.0" and the ecosystem was stable as far as I tested it. The IDE (Zerynth Studio) can be a little bit improved, but it works well enough.
Zerynth is neither free nor open-source but every new user gets a welcome pack with 10 Zerynth VM licenses with FreeRTOS (5 Starter and 5 Premium) for free (more info here). If you need to register more sensors, you can use the store to purchase the additional licenses.
Important NOTE: I didn't get any money to promote Zerynth, I just wanted to use Python to connect the ESP32 directly to the Google IoT Core and this was the only option that I've found. If you know another one, please comment this post or send me a message. Thanks!