I want to run not only filename.cy.js but also filename.js. How can I achieve this (V10+)?

You can set the

specPattern

in your config to include both. If it's not populated now, then it is using the default, which expects

.cy.{js,jsx,ts,tsx}

at the end. More details are here: https://docs.cypress.io/guides/references/configuration#e2e