Actually now that I learn the hard way, snap is now the standard way to install applications in Ubuntu (at least for Ubuntu 20.04). The applications data directories are located in /snap/ (actually they are compressed filesystem contained in /var/lib/snap mounted in /snap). The directory ~/snap is meant to store personal data, it has several functions including data containment for each app and data snapshots (automatic during app upgrade, can be manual too, now I know).
This problem is likely to be reproduced for all future Ubuntu users.