unable to install plugin

I'm running Chrome OS Version 86.0.4240.198 (Official Build) (64-bit), and I'm trying to test out Arduino Create with an Arduino robotics kit. I'm running the 30 day free trial. This is a dry run for teaching an Arduino Robotics class next semester, and my students all have Chromebooks. So, I need to figure out how to make everything work with Arduino Create on Chrome OS before I sign up for subscriptions.

I'm able to open the web editor and write sketches, but I can't get the plugin installed that would allow me to communicate with the Uno clone that came with the kit. I can download the plugin (from here: https://create.arduino.cc/getting-started/plugin/download), but then I get a .tar.gz file that I can't open. The instructions say to just double-click and run it, but my Chromebook doesn't know how to open that file type. I get the feeling I may be missing something obvious here, but I can't figure out how to get the plugin to run.

Right, so it turns out it was trying to get me to install a Linux plugin, which is not helpful. Meanwhile, the app just needed to be reset to start communicating with the boards.

So that was a blind alley; if anyone reading this is working on the arduino create web editor; please fix the bug that tells Chrome users to download the Linux plugin. I wasted an enormous amount of time trying to make something work that was irrelevant to the problem.

So is it working without the linux plugin? How?
I had the same problem but turned on Linux beta in the chromebook settings and was able to install that file that you said you downloaded. But yet I still cannot connect to the Arduino board.