If you are not seeing your Era Loaned Units, force restart the game and they will appear.
Summary by GAC Film Room of an official EA / Capital Games post. The official post is the final word; details can change after it goes up.
The four units needed to unlock Galactic Legend The Mandalorian and Grogu are Mercenary Guard Droid (B1) and Adelphi Ranger at Era Level 74 or Relic 7, IG-12 & Grogu at Relic 10, and Snowtrooper Commander at Relic 8.
The Mandalorian and Grogu is a Light Side Galactic Legend Attacker and Leader for New Republic who stacks the un-dispellable On the Run debuff, takes a Grogu turn and a Mando turn back to back, and resets the team with the Ultimate Fire Up the Drives.
A limited time Era Battle for Adelphi Ranger and Mercenary Guard Droid (B1) with 7 tiers from any investment level up to Relic 9, landing near the end of the year.