The BBC website apparently still requires Flash for some of its video content - specifically, for the Davis Cup doubles match against France that GB are currently playing - so I just worked out how to get Flash working in Chromium on my Debian laptop. My laptop is always following Debian 'testing', which currently maps to 'stretch', aka the future Debian 9.
neil@neil-laptop:~$ cat /etc/os-release PRETTY_NAME="Debian GNU/Linux 9 (stretch)" NAME="Debian GNU/Linux" VERSION_ID="9" VERSION="9 (stretch)" ID=debian HOME_URL="https://www.debian.org/" SUPPORT_URL="https://www.debian.org/support" BUG_REPORT_URL="https://bugs.debian.org/"
A little searching was needed, because https://wiki.debian.org/FlashPlayer and https://wiki.debian.org/PepperFlashPlayer/Installing don't cover Chromium on Debian 9/stretch; but there is Ubuntu-focussed information at http://ubuntuhandbook.org/index.php/2016/11/new-pepper-flash-installer-for-chromium-firefox/, and a PPA at https://launchpad.net/~jonathonf/+archive/ubuntu/pepperflashplugin-nonfree/+packages, that happily works for Debian 9 as well.
So with those resources, the procedure that worked for me was to:
.debfor Xenial, from that PPA page
try installing it with
dpkg -i, to be told that it needs
apt-get install jq