if i wanted to allow for a non-view html page (index.html) driven by thymeleaf in a grails app, do i just drop it directly into the grails-app/assets folder? — i tried adding this to my grails app, but its getting a 404. when i go to /index.html. -->

spring:
  thymeleaf:
    enabled: true
    mode: HTML
    prefix: file:/assets/templates/
    suffix: .html
    cache: false

localhost:8080/index.html -> 404.

https://stackoverflow.com/questions/72995986/is-there-any-way-to-use-thymeleaf-in-grails-instead-of-gsps the vast majority of users use GSP, so thymeleaf is going to be harder to find examples on.

I was looking at that earlier but it uses the deprecated webapp folder idea?

I'd look at GSP, it is the grails view technology used in most projects. https://gsp.grails.org/latest/guide/index.html