A little more information has been gleaned about the new show, from an article posted on TV Insider. 

We can expect a premiere on MGM+ in December, though no exact date has been released, and there will be six 45-minute episodes. So far no set photos have snuck out, but there is always lots of promotion for flashy new shows, so we have that to look forward to in the fall and winter. 

Tom has been cast in, and already shot, a new MGM+ series based on the Robin Hood legend. The show was described in TVLine, by showrunner John Glenn, as a “sweeping, romantic adventure, a modern take of the classic tale that brings historical authenticity, psychological depth, and a heightened focus on the relationship between Rob and Marian.” Tom will have a recurring role in the first season as Rob's father, Hugh Locksley, a Saxon forester.