Maybe extracting the folder from the zip file after downloading it. The folder name must be " argon " , then zip ot and upload it to the mod directory at your server, and that is what should appear under the website /home/serenity/john.serenitytoo.com/mod/argon-theme/ and then try to install it under the administrator control panel.

must be like this. /home/serenity/john.serenitytoo.com/mod/argon/  

The Argon Theme is only compatible with elgg 2.3.x:

https://elgg.org/plugins/3110405

I don't have an estimated date for a new release compatible with elgg 4.x

Simple enough. Installed elgg 3.3.21 and vision_theme AOK!!!

I spoke too soon. Side panel DISAPPEARS on Android phone.

This all started because the Hamburger button on android to bring up the menu is often impossible to execute on a phone or android tablet. Since those devices represent a substantial portion of devices in use this is VERY important. I've tried it on a Samsung S9 and a Vankyo 7 inch tablet

Try it on even YOUR site elgg.org and see what I'm talking about.