Last_updated for the Entur should only change when data changes.
During an Internet or API outage, the last_updated continues to update.
I would like to use this sensor to detect when the Internet/API is down and data provided by the integration is unreliable
Last_updsted is often used to provide data points for graphs on sensors that do not change often, so that functionality should stay.
Other integrations have a last_changed attribute too that does what you look for, so I suggest that instead.
And remember to vote for your own suggestion! 
Thanks for the suggestion, vote has been given 
The last_changed appears to do the exact same for the Entur integration, have I misunderstood something?
I pulled my ISP fiber cable from my gateway and the Entur Integration continued to update both the last_updated and last_changed attributes
That sounds like an integration “bug”.