Problems Chromebook users might encounter

Samsung CB Pro on v.91 ChromeOS, Charging while running Monitor. Don't charge your Chromebook while trying to run the monitor. You can waste a day of hard work trying to find out why you Serial.println() are producing duplicate/overlapping output. The CB Pro charges via USB-C of which there are 2 ports.

Toshiba (2014) on v.87 ChromeOS. Charging while downloading a sketch. Don't charge you Chromebook while trying to download a sketch. You will/may get: "3020 timeout after 400ms" errors. Not every download but often enough to make you stop. The Toshiba CB charges via a separate charging port.

The above two problems went away when I stop charging my Chromebooks. Not conclusive proof but sufficient that I will avoid this in the future. YMMV

Yup, another guy had the same issue last week.
It's cool of you tp take the time to share this though. I'm sure it will help someone.