Certified GKH Gardening Expert
It will be very difficult to find something that will go well under pines, since they are allelopathic. This means that they tend to kill any plants around its, immediate, area.
Your best bet would be to try acid loving plants. Though many will not work, you may come across something that will.
These articles will help:
https://www.gardeningknowhow.com/garden-how-to/info/allelopathic-plants.htm This article will help you to get started: