I my case the js file is nont being loaded for some reason and I am trying to extend the POS component even though the file is correctly loaded:

'assets': {
    'web.assets_backend': [
        'my_module_name/static/src/js/cash_move_popup_patch.js',
    ],
    'point_of_sale.assets': [
        'my_module_name/static/src/js/cash_move_popup_extend.js',
    ],
},

Here is the file itself:

/** @odoo-module **/
console.log("Patch file loaded")
import { patch } from "@web/core/utils/patch";
import { CashMovePopup } from "@point_of_sale/app/navbar/cash_move_popup/cash_move_popup";

patch(CashMovePopup.prototype, 'custom_cash_move_popup_patch', {
    setup() {
        console.log("Custom Patch: CashMovePopup has been called.");
        // Prevent the original setup method from executing
    },
});

The console logs are not showing

you need to depend 'web' module to make it works. because somehow your modules are loaded before 'web' module.

For what is worth, I think the issue was related to some kind of cache somewhere: restarting from a clean checkout of the development environment on a different machine did not exhibit the problem, and thus, after spending some time to cleanup whatever seemd like a cache in the original environment, I eventually got it working there too.

Sorry for the noise and thanks for reading.