Steam for Linux is designed to run on GNU/Linux systems, and does not support use of non-GNU core utilities.
But, since avoiding the --quiet option is straightforward, the latest Steam update (2021-09-13, 1631572918) avoids it anyway.
This should not be interpreted as a commitment to support non-GNU core CLI utilities in the future. The only officially supported platform is (still) the latest Ubuntu LTS.
Closing per the last comment.
Nothing extracted yet.
In steamwebhelper.log, the steam runtime heavy tar.xz failed to be verified because the "--quiet" option from your md5sum command is used and the busybox version of the md5sum command does not have the "--quiet" option (I created a wrapper to remove this option, then I did hit the libcups hard dependency error, see the corresponding ticket).