"Apply All Layer Masks"

Try this script. Layer sets and their contents are not processed, this script is intended for "flat" layer structures

/*
Apply Layer Mask To All Layers.jsx
v1.0 - Stephen Marsh, 13th January 2022
https://community.adobe.com/t5/photoshop-ecosystem-discussions/quot-apply-all-layer-masks-quot/m-p/12655017
Note: Layer sets and their contents are not processed, this script is intended for "flat" layer structures
*/

#target photoshop

function main() {
  
    app.activeDocument.activeLayer = app.activeDocument.layers[app.activeDocument.layers.length - 1];

    // Loop forward over top level layers
    // for (var i = 0; i < app.activeDocument.layers.length; i++) {
    // Loop backward over top level layers
    for (var i = app.activeDocument.layers.length - 1; i >= 0; i--) {
        try {
            app.activeDocument.activeLayer = app.activeDocument.layers[i];
            applyLayerMask();
        } catch (e) { }
    }

    function applyLayerMask() {
        var iddelete = stringIDToTypeID("delete");
        var desc352 = new ActionDescriptor();   
        var idnull = stringIDToTypeID("null");
        var ref64 = new ActionReference();
        var idchannel = stringIDToTypeID("channel");
        var idchannel = stringIDToTypeID("channel");
        var idmask = stringIDToTypeID("mask");
        ref64.putEnumerated(idchannel, idchannel, idmask);
        desc352.putReference(idnull, ref64);
        var idapply = stringIDToTypeID("apply");
        desc352.putBoolean(idapply, true);
        executeAction(iddelete, desc352, DialogModes.NO);
    }
}
app.activeDocument.suspendHistory("Apply Layer Mask To All Layers.jsx", "main()");

https://prepression.blogspot.com/2017/11/downloading-and-installing-adobe-scripts.html

What's the structures of layers in the document, like for ex. no layer sets?