@Tomas5 I used walkie-talkies with headsets for paragliding, but it was always a hassle with the cables. Today you can get 4 walkie-talkies with Bluetooth headsets for under 200 €.
But if you really want an easy-to-use outdoor solution, you’ll have to spend more: go for Milo, it simply works → https://www.okmilo.com/de/reviews
Bluetooth isn’t great for this use case: it has too much latency, limited range (10–15 m max), and it’s designed for point-to-point streaming, not low-latency group talk. That’s why outdoor intercoms like Milo or Sena use their own mesh/radio protocols instead of Bluetooth.