X11 (and indeed Java) needed on a cluster?

I hate to demonstrate my ignorance...

We have been donated 12 nodes to create a mini R cluster. I am "IT" not an end user. While configuring the system for an "openblas" install (as requested), I notice I have to add an awful lot of extra packages. The nodes obviously don't have a Gui so initially I thought "no need for that X11 stuff" and use "--with-x=no"
However I am pretty sure I am wrong and packages that generate graphs and stuff will use it.
Similarly if I skip java (and I don't know if I can), will that have knock on effects for end users?

One final question. My "capabilities()" shows

> capabilities()
       jpeg         png        tiff       tcltk         X11        aqua 
       TRUE        TRUE        TRUE       FALSE       FALSE       FALSE 
   http/ftp     sockets      libxml        fifo      cledit       iconv 
       TRUE        TRUE        TRUE        TRUE        TRUE        TRUE 
        NLS     profmem       cairo         ICU long.double     libcurl 
       TRUE       FALSE        TRUE        TRUE        TRUE        TRUE

(I installed all the stuff I am questioning if I need) , However I notice cairo = true but X11=false. Will the X11 have knock on effects for the end users.

If this forum does not deal with the above (or I ask really stupid questions) I apologize.
My end users are data scientists (epidemiologists) and they produce lots of graphs and stuff (currently doing covid stuff)
./configure --prefix=/opt/R/4.0.2_vanilla --enable-R-shlib --with-cairo
(although i think the cairo option was not needed)
openblas is my next step

This isn't answering your question directly, but you could take a look at our recommended instructions for installing R from source at https://docs.rstudio.com/resources/install-r-source/

Or you can make your life even easier and install the pre-compiled binaries for your OS from https://docs.rstudio.com/resources/install-r/

For more information about how these binaries were built, see https://github.com/rstudio/r-builds

If you have a valid DISPLAY when you run capabilities, then X11 is true. If DISPLAY is not set, then X11 will show up false.