I dont trust those cheap chines handsets, i hear most of what you see about them on yt are buyed reviews and that they resonate on all sorts of frequency's beside what they should, but thats just anecdotal.
Besides that i guess that they have some sort of EW off switch or worse u hit em with the right data package over the air and they just start broadcasting your location on max power till the battery is dead.
To be real with radios that arent fully analog there is always the possibility of them having backdoors in the modem firmware.
I just think its to good to be true that the chines flooding the marked aggressive with capable handsets that are so incredible cheap that everyone can get one or more than one.
I heared parts of the firmware are replaceable with opensource firmware, maybe thats an option. But i bet there will be some software on the device that isnt replaceable, something bios or modem firmware alike.