(Broken or incompatible)

Hi guys! I know that 1.21.9 changed the pack.mcmeta syntax and I've adapted mine to it, with the idea of keeping the back-compatibility.
{
  "pack": {
    "min_format": 69,
    "max_format": [69, 0],
    "description": "Working Backpacks\nUltroGhast",
    "pack_format": 55,
    "supported_formats": [
      48,
      69
    ]
  }
}```

Still, even though Misode’s generator and I agree that the syntax is correct, the game considers it incompatible.
The logs throw an error `Pack key supported_formats is deprecated starting from pack format 65. Remove supported_formats from your pack.mcmeta` (weren't old fields supposed to be just ignored by the new versions?) Even if I do, then the problem will be with pack_format.

What should I do? I really do care about back compatibility