Is there a no-code way to add a widget to a website that does not require changing the website's code base?

Is there a way to add a widget to a website (e.g. a small button that hovers in the corner that you can click to be redirected to another site) without having to add a code snippet like e.g. intercom requires?

Context: looking at a user base for a service that all don't know how to code or change their website code base, but would benefit tremendously from a widget on their website.

Thanks!