The legal definition of fair use isn’t precise, and whether something is or isn’t often depends on the context and intent. Using zoom or video chat to play MTG or have a socially-distanced tournament is almost certainly fine, because the ‘copies’ are temporary, valueless, and only exist to facilitate the use the cards were intended for at a distance.
For-profit streaming, where someone plays MTG on twitch or unboxes cards on youtube, is a more grey area. Technically it’s “performing for donations”, and WotC could certainly shut down or sue on copyright grounds, but it would be up to the court whether the performance was transformative enough to be considered fair use. Most companies that rely on sales to a fanbase understand that shutting down all the free promotion would be counter-productive, though they will take action on things they think may damage their brand.
