Dallas Mavericks fans are still livid the team traded away their superstar, Luka Doncic... and a group of fans are taking their displeasure to the streets -- 'cause TMZ Sports is told a billboard calling for general manager Nico Harrison's job is making its way around town before Wednesday's highly anticipated matchup with the Lakers.
Dallas Billboards -- in partnership with Southwest Mobile Advertising -- tells us an anonymous batch of donors reached out to them to commission the sign in opposition to the front office staffer and team owners, the Adelson/Dumont family.