I am interested in that issue too.
I'm planing to get an IodeOS phone and i highly oppose the idea of "scan-on-device" / cliwnt scanning backdoors in Software.
Not only having a single App with such a backdoor in, but the base OS having one, is even worse...i didn't know this was law in france already.
Even if i am not in danger to be targeted in an legal investigation, does such a backdoor not pose a great risk to be hacked by criminals via that way too?