I think signal/OTR has e2ee support for pretty large groups. The kid was using airport wifi for this right? I'd guess public airport wifi installs some backdoo

I think signal/OTR has e2ee support for pretty large groups. The kid was using airport wifi for this right? I'd guess public airport wifi installs some backdoored SSL cert and is generally monitored (and you probably agree to this ToS when you use it) - you may even agree to not make jokes about planes - I wouldn't be surprised.