Hi!
Just to confirm, this may be an outdated version of the package you're talking about? The newest version is this: https://pastebin.com/h9fyzJcq Which has a few other adjustments in it that work for other RTL languages and fixing ligatures in general, hence the rename.
Additionally, there is an "RTL" boolean under the "Beta" foldout in the Super Text Mesh inspector that can be used in tandem (or not, based on usage) with this component.
If multiline text (as in, multiple lines in a single text box, not a chain of dialogue) continues to be a problem, I'll give this a closer look! Make sure "break text" is disabled as that will make text split when a space is encountered. I might need to add specific Arabic punctuation to the internal punctuation list if I haven't done so already to keep line breaks happening at good times, or adjust the fixer script to accommodate for this.
A screenshot of your Super Text Mesh object's inspector and appearance in the scene view and some sample text for me to use would be a massive help for this!