It seems like Bluetooth is safe, and using a phone with a headset might be the safest combination.

https://youtu.be/AnOm_nTupGg

The video says that bluetooth operates at higher frequency but about 1000x lower power, which makes a lot of sense. Having a small device near your head broadcast a message a few feet seems much lower risk than having to broadcast all the way to the nearest cell phone tower.

Another thought: my phone and provider (Pixel 2, Google Fi) will automatically use WiFi for calls when available. I wonder if that mode is significantly lower radiation for the same reason (shorter distance to cover, so the signal doesn't need to be as strong).

Bluetooth seems safe, and simply holding the phone up to your head the old fashioned way also seems safe. The article is trying to drum up fear when there is no evidence of real danger.