@prudhomm it seems that there is a missing directory in the toolboxes docker image:
docker run -it --rm ghcr.io/feelpp/feelpp-toolboxes:feature-toolboxes-v0.110.0-alpha.3-ubuntu-20.04
Starting with UID : 9001
chown: cannot access '/feelppdb/testcases/': No such file or directory
To run a command as administrator (user "root"), use "sudo <command>".
See "man sudo_root" for details
I guess this is not a big issue