You were on the right track adding reports as a list within the Truck Data type.
Assuming this page type of content is Truck and you are looking at one Truck at a time, the Repeating group source would be, "Current’s page truck Reports"
What would be helpful is to share a screenshot of your RG source.
I of course use a “display data in Popup + RG Group” workflow.
But now my “Reports” data field inside of TRUCKS is a LIST, the options that i have are different and i can’t find the solution to display each reports in different rows.
I think you will need a RG that display your Truck Reports, and then you can select one of that report and display its data on the side. I suggest you use a state to select a specific report.