UX: Login/Sign in modal for scripts turned on, separate page for when turned off

As the title says. I'm thinking of doing a progressive enhancement where if a user has Javascript turned off, a "sign in" anchor tag will take them to a separate page. If Javascript is turned on, preventdefault kicks in and instead it opens a modal on the same page - which means less navigation. Also combining this with the cutting edge framework Qwik would make the added javascript not a big deal at all since it lazy loads. Is this a good idea for UX? (also don't mind the cobbled together form, this isn't meant to illustrate perfect UI but rather just show the idea quickly)