For sure, can you point me to the labor law stating that company issued equipment is primarily for the personal use of the employee? I couldn't find anything at the federal level.
My info was out of date but pre-Dec 2019 (Caesars Union Suit), electronic communication channels were treated like break rooms- if they aren’t already restricted to only work chat, and you could shoot the shit, then they can’t block or specifically spy (or appear to spy) on protected union activity. Post that ruling, I don’t really understand where the line is. Apparently if there is no other way to communicate outside of work with your co-workers, then they have to let you do it. Maybe you could argue that’s the case during coronavirus unless you can easily get everyone’s personal emails. Shrug
Except maybe by word of mouth spread the existence of external forums for communication that don’t involve leveraging company paid resources and some kind of entitlement to use said resources for non-company purposes. Using external resources and word of mouth may not be the most convenient result but it’s realistically fair.