Why not just use Airthings, don't use their service, and own your data.

They say in the license if you use their service (i.e. you upload your data to them) they own it. But if you don't, you own it. Seems fair to give them their data if they are going to store it for you and provide you an app and website to view it.

They publish a github repo to let you download direct from airthings (not using anything cloud) and graph it with graphana or whatever you want.