I've used outdoor soil sensors from mydevices.com. Once I told them to stop trying to upsell me on the Lora gateways and use Helium, its worked flawlessly. Its been like 6 months and the battery still registers 100%. Reports every 15 minutes and the data credits find their way to 3-4 different hotspots in the area. Source: almost 3 years ago

Another site that shows data transfer activity: https://mappers.helium.com/ Here's some examples of potential uses: https://www.lonestartracking.com/ (track anything anywhere) my brother wishes he had one of these when his maintenance truck stolen. https://mydevices.com/ (plug and play IOT sensors) I'm talking to one of my customers who is a landscape architect, he wants to monitor his larger landscape projects... Source: almost 3 years ago

Esp32.net has a bunch of additional references, projects, and places to gather information. Source: almost 3 years ago

Closest thing is the ESP32 from Espressif Systems See ESP32 link for details. Since you specifically asked for open source, so some tinkering and compile is required. Source: about 3 years ago

There's also many more dev boards, chips and modules listed here, though they may not necessarily have platformio IDs. Source: about 3 years ago