Hello everyone,
Firstly, I apologize for my poor english cause I’m French. Secondly, I will try to explain step by step my little problem.
Triying to install anbox for personal use (and avoid to buy a smartphone) with my debian distribution (updated just before), I follow their guidelines and install the snapd package (https://packages.debian.org/stretch/snapd). I add the good mirror as indicated (deb http://ftp.de.debian.org/debian stretch main ) in my sources.list and, through synaptic and I found the last version of snapd (_2.21-2+b1_amd64) that it was missing before.
Launching the installation, I got a little message saying that two process had to be shutdown (xscreensaver) because, they were attached to another package. After that, another message warned me that other dependencies would be modified. My bad, I didn’t chose to be asked at each modifications… and I can’t remember all the packages that they have been downgranded, I think.
After that, I have tried to install anbox but… it was incompatible with my distribution. Funny, isn’t it ? But, when I want to launch firefox (52), I got an error… again and again that I have never seen before.
(firefox-esr:15764): GLib-GObject-CRITICAL **: g_object_ref: assertion 'object->ref_count > 0' failed
ExceptionHandler::GenerateDump cloned child 15785
ExceptionHandler::SendContinueSignalToChild sent continue signal to child
ExceptionHandler::WaitForContinueSignal waiting for continue signal...
Failed to open curl lib from binary, use libcurl.so instead
Afer some googling, there was a chance : it’s an already known bug… but without solution. It seems to that the snapd installation made too many modification to my version of firefox. And, other clue, Libroffice was uninstalled, too. (EDIT: And when I try to reinstall Libroffice, I got a mistake cause of broken dependencies.)
So. Here I am to ask some help if you have. I know where find the last changes in synaptic… But, I used a terminal so I don’t know where to find all the modifications made by snapd or his dependencies. This is my only idea to repair my mistakes. If you have another, it will be helpful ! 
Have a nice day,
