just practice serving underspin against an lp player and then learn to attack topspin or no spin when it comes back. that is a good way to start on how to learn to attack against LP. you would need to adjust on how hard you would brush the ball.
I use to play with LPs and IMO there are different camps of type of LP players. Some of them largely just stick it out there and kinda block the ball. For these people, yes do that strategy.
Then there are some LP players who have practiced attacking backspin serves with their LPs which is very easy. These shots typically have more pace & placement but yes the same concept applies that it's topspin going back to them.
Because I didn't want to be too predictable as i saw people started to expect topspin going back to them, i because to aggressively jab at the ball with a pushing motion which would essentially deaden the ball and/or produce weird balls. Some people really struggled with this variation when they were always expecting topspin.
To the OP.
I don't play LPs anymore but my training partner who got a lot of practice vs me (kinda what NL was suggesting. practice a lot vs it). He would simply soft loop ball after ball getting them in while i chop blocked.
So it would be
me - chop block
him - soft loop (ie - high arching loop that clears the net easy and is actually really spiny. Key is this should be a shot you can hit in 9 times out of 10)
me - chop block with a ton of topspin coming in.
I eventually adapted thinking if there's this high arching topspin ball coming over, i need to step around that ball and attack it. Although you have to really close down on the angle because the soft spiny loop is easy to kick long.
Anyways, like I said, i don't play LPs anymore. But if I were you? I'd practice generating my own spin and seeing how many balls vs backspin you can loop in safely over & over. If the chopper pops one up too high? Then you go for a power loop. ie - a put away shot.