The Gears 5 Lost Outsiders side mission crops up once you've made it to the snow-filled open world section of Act 2, and at the beginning or end of the New Hope mission during the Gears 5 campaign you'll discover the Outsider Campsite. This contains a collectible titled Lena's Journal, which will then get you started on the Gears 5 Lost Outsiders mission. To complete this mission you need to go and find two communications towers, so here we have all of the Gears 5 Lost Outsiders locations you require to get it done.
Gears 5 Lost Outsiders: East Tower Substation
The north tower is closer, but you won't actually be able to access it until you've visited the East Tower Substation first. Head to the south-east corner of the map, just up the path from the main objective, and interact with the door to open it.
Inside, you'll find Lena. Unfortunately, she's succumbed to the cold, but in the adjacent corner is the Security Memorandum collectible which will give you the access code for the North Tower Substation. Leave the substation and hop on the Skiff to head north.
Gears 5 Lost Outsiders: North Tower Substation
In the north-west corner of the open world area is where you'll find the North Tower Substation, and once again it's down the path from the North Comm Tower. Interact with the keypad by the door to pick up Lena's Scribbles and gain access.
Inside, the substation has the same layout as the previous one. As you step inside the second room, Norsko — who is now a Juvie — will leap down and attack you, so have your Gnasher ready to blow his brains out. Instruct Jack to open the safe in the corner on the left-hand side to obtain the Seeker upgrade for his Shock Trap ability.
Voila! You've completed the Gears 5 Lost Outsiders mission and can carry on with the main objective.