- You did not add a NEWS entry and did not update the manual in your patch.
- There are many compiler warnings emitted when compiling Org with your patch

> +(defun org-latex-inline-src-block--minted (info code lang)
> +  (let ((mint-lang (or (cadr (assq (intern lang)
> +
> +(defun org-latex-inline-src-block--listings (info code lang)
> +  (let* ((lst-lang (or (cadr (assq (intern lang)

The docstrings are missing in the above.

> -Alternatively,
> +There are two fancier options for fontification.
> +
> +The first fancy alternative,

I am not sure why, but the word fancy feels slightly annoying here.

> +
> +The styling of the engraved result can customised with
> +`org-latex-engraved-preamble' and `org-latex-engraved-options'.
> +The default preamble also uses the tcolorbox LaTeX package in
> +addition to fvextra.

Since engraved is not entirely relying on LaTeX options, a lot of
customisation is not mentioned in this docstring. AFAIU, color
customisation is only possible by changing defcustoms from engrave-faces
package.

Another related note is what is going to happen in beamer export with
dark background. The default face mapping in engrave-faces is using some
kind of light theme, which may lose all the contrast on not-light
background.

> +\\renewcommand\\theFancyVerbLine{\\footnotesize\\color{black!40!white}\\arabic{FancyVerbLine}}
> +
> +\\providecolor{codebackground}{HTML}{f7f7f7}
> +\\providecolor{codeborder}{HTML}{f0f0f0}
> +\\providecolor{EFD}{HTML}{28292e}

> +(defcustom org-latex-engraved-options
> +  '(("commandchars" . "\\\\\\{\\}")
> +    ("highlightcolor" . "white!95!black!80!blue")
> +    ("breaklines" . "true")
> +    ("breaksymbol" . "\\color{white!60!black}\\tiny\\ensuremath{\\hookrightarrow}"))
> +  "Association list of options for the latex fvextra package when engraving code.

It feels that codebackground, codeborder, and EFD should be customizable
by org-latex-engraved-options.

> +(defun org-latex-generate-engraved-preamble (info syntax-colours-p)

Docstring?

> +(defun org-latex-inline-src-block--engraved (info code lang)
> +  (if (require 'engrave-faces-latex nil t)
> ...
> +    (message "Cannot engrave inline src block, `engrave-faces-latex' is unavailible.")
> +    (insert (org-latex--text-markup code 'code info))))

Why message instead of error?

Best,
Ihor