The system-wide /tmp is not accessible by strictly-confined snaps, so
/tmp/chromium-home won't work either.
In any case this looks like a limitation hard-coded in snapd, which
won't create $SNAP_USER_DATA if $HOME is not in /home. So this is not
specific to the chromium snap. I'll add a snapd
Thanks for the suggestion, and you're right, your summary is better.
I tried the following (with various permutations).
sudo su -l -s /bin/bash www-data
mkdir /tmp/chromium-home
HOME=/tmp/chromium-home /usr/bin/timeout 60 chromium-browser --no-
sandbox --headless --disable-gpu
