Only one team confirmed so far for DTM 2021, GruppeM Racing, a team from Hong Kong that ran Raffaele Marcielo (who won) and Maro Engel in the GT World Cup at Macao in 2019.
In 2018 they ran drivers like Raffaele Marciello, Patrick Niederhauser, Nico Bastian and Markus Pommer in the (Blancpain) Asian GT Series. Tim Sugden, Jules Simkowiak and Maximilian Buhk (who also ran in 2018 sporadically) ran full time for them in '18 with also a guest race for Marciello & Maximilian Götz.
In the International GT Challgenge (by Pirelli) they entered at Bathurst this year with Maximilian Buhk, Felipe Fraga & Raffaele Marciello in the car (they finished 5th). In 2019 they ran Maximimilian Buhk full time and Raffaele Marciello almost full time with Maximilian Götz, Lucas Auer & Maro Engel featuring as 3rd driver in that car. At Monterey the entered a second car for Maro Engel, Yelmer Buurman & Luca Stolz. In 2018 they entered Tristan Vautier, Maro Engel & Raffaele Marciello at Suzuka.
They have been very competitive in this series winning at Suzuka in 2018 and winning at Bathurst in 2019. Each time Marciello was behind the wheel.
They always entered Mercedes GT3 cars and will also enter those in DTM.
They are a very good addition for DTM, very good team and I think it's highly likely that their drivers will be chosen amongst the drivers who already drove for them in the past. Marciello seems their preferred driver and I assume that people like Götz, Buhk, Buurman or Engel are also in a great position to get signed for DTM. And Lucas Auer, who also did one race for them, has DTM experience. I don't know if they will run 1, 2 or 3 cars but if I would guess on their line-up I would say that Marciello & Engel are highly likely in case of a 2 car line-up.