It should be "trips", as "poverty line is singular.
The meaning seems to be a complex metaphor. "The poverty line" is the level of income below which you are officially "poor".
In the UK, millions of people are still below the poverty line.
But "high-speed-digital line" is a physical wire or fibre that connect you to the internet.
To "trip over" means catch your foot on something and stumble or fall.
Literally the sentence is impossible (a poverty line isn't something that can trip). So here it must reference to "people who are poor". The "digital line" represents "access to the internet" and "trip over" represents "fail to do something smoothly and easily"
So the metaphor means "people who are poor find it difficult to access the internet".