I would go for AWS personally as they have a lot of resource and support including practical documentation and example for LorWAN & ML.

You can start by looking at this quite comprehensive blog https://aws.amazon.com/blogs/iot/connect-your-devices-to-aws-iot-using-lorawan/

I would also recommend you to check the twitch.tv channel https://www.twitch.tv/aws and https://www.twitch.tv/amazonalexa and search for iot streams where you can ask live questions if you get stuck.

These resource has been useful for me many times in the past (especially for Amazon Alexa, AVS IoT implementation)
Hope that helps and good luck.