Minecraft Java Edition Datapacks – How to Create a Datapack with a Void Dimension

I have recreated your datapack on my own testing world and I loaded your loottable and indeed I found that there was no loot generated.

I checked your syntax against the guide on this webpage and it checks out.

I finally checked the log file and found a Json parsing error on the function "set_data". This seemed strange to me at first, since this exact function was specified in the guide, but then I realised that data is no longer in the game. You can't specify different stone types with different data values, because each stone type has it's own name now.
I removed the entire function and now I can spawn a chest with a stone block in it, using the command which you provided. This is the new loot table:

{
    "pools": [
        {
            "rolls": 1,
            "entries": [
                {
                    "type": "item",
                    "name": "minecraft:stone",
                    "weight": 1
                }
            ]
        }
    ]
}

I tried to see if tags would work to define different items in one entry, but that didn't work, so if you want to have a random stone type for example, then you will have to define each one individually.

The /debug command is useful for measuring performance. Use /debug start to start the profiling, wait a while, then /debug stop to end.

This produces a file in .minecraft\debug breaking down how long everything took to run. Kind of like the F3 pie-chart, but for the server rather than the client.