Below the game table, there are options to change backgrounds and fonts. This won't change card fonts, however. There are zoom options on desktop, too.
If you're playing on mobile, I'd suggest making sure tooltips are available, and clicking any card you are having trouble reading. Obviously don't do this during the buy phase on your turn, since you may buy something you don't actually want.
If Dark Edition has accessibility problems, perhaps it's best we don't use it for Arena in future. Apologies, it didn't even occur to me that DE would cause these issues when I suggested it as a new format.
