renv::use() is described as "a useful way of sharing standalone R scripts", specifically Rmd and Qmd documents. However, the presence of renv:: suggests that the scripts will not knitr or render unless renv is already installed, is that correct? If so, how can this be done in a standalone way, without requiring other files to bootstrap the installation of renv?
That's correct. While you still need renv in order to render the document, it helps take care of installing specific versions of package dependencies before running a script or R Markdown document.
That is, the document is not "standalone" per-se, but you can feel more confident that the document, when executed, will use a fixed set of package dependencies as declared in the renv::use() invocation.