I have never used a scaleway c1 for testing. I avoid them due to the arm architecture. I've gotten it to build on the VC vps and the C2s though. The only quirk I've found is that scaleway enables auto updates which is a conf file that messes up the flow of the installer.
The offending files are in /etc/apt/apt.d
The main file is the unattended upgrades configuration that needs to be removed. I usually remove everything in that folder, but I just test and don't use it for production and that might remove something you might regret later on