Finally! You can install the latest Arduino IDE and upload code to an Arduino on a Chrome OS device!!! I've documented the entire process. It's hacky, but works well after the install. **
Programming an Arduino from a Chromebook with Crostini – Likely to be Forgotten
Install Arduino on Chromebook
Install Arduino on Chromebook
Install Arduino on Chromebook
Setup Arduino
Howto: Setup Arduino on Chromebook | Tom W Wolf
Program Your Arduino from Your Chromebook - Make:
Arduino IDE on Chromebook - YouTube
Now free! Get the Arduino Create app for Chrome classrooms
Use Arduino with Chromebook – Arduino Help Center
Introducing: Arduino compatible IDE for Chromebook and ChromeOS - General Discussion - Arduino Forum