Since 1.15 the chest models have changed, which broke the chest textures.
As chests are entities, there’s no JSON file describing the model, it’s hardcoded in the Java code. The only way to change it would be through a mod.
To fix the chests in versions 1.15+ I decided to create add-on packs with the existing Vanillaccurate chest textures but with the correct layout for later Minecraft versions.
If you’re playing any version from 1.15 on, you just have to download any “new chests” pack with your desired resolution and load in on top of an existing Vanillaccurate pack with the same resolution.
HardTop Vanillaccurate 