Tried to keep it simple... showing warning to all admins/super users in reporting/admin UI:
And simple page showing more info
didn't add any of the piwik is now matomo image etc as didn't want to put it under GPL and I would say it is better to keep it straight to the point.
Changed it to at least view access. Would in theory need to show super user email login names or their email so they can ask them to update.