There are some omissions in the article
https://developer.toradex.com/knowledge-base/torizon-qtcreator
To build application for target on the developer machine Configure build environment
docker run --rm -it --privileged torizon/binfmt
test
docker run --rm -it arm32v7/debian arch
otherwise
sh: 1: /usr/lib/qt5/bin/rcc: Exec format error
Building the container
instead of
$ docker save qt5-target | ssh torizon@<IP> docker-load
run
$ docker save qt5-target | ssh torizon@<IP> docker load