I got some news.
I tried today again to take some photos, and it was working. So since I have another issue (which is described here Can't make a call using Signal or WhatsApp since migration to v1.0), I also tried to check if it was still the same.
So basically I still can’t make a call with SIgnal and/or WhatsApp, and I realised that my camera is not working after an unsuccesful call. It’s like if my failed call with SIgnal makes the camera module unavailable.
After restarting the phone, and as long as I don’t try to make another call, looks like there is no problem with the camera.