From this page of the Watch Dogs Legion guide, you will learn about all the Tech Point locations in Southwark.
HMS Belfast [1]
The Tech Point is located on the highest deck of the ship. Use the drone to get there.
AYW Imports [2]
The tech point is hidden on the roof of the building. You can easily drop a Spiderbot in there, or fly a drone.
Queen's Walk [3]
The Tech Point can be found in a vent shaft, right next to the river. To get there, you need to open the locked hatch. Use the drones flying around to unlock the circuit. Then use the Spiderbot.
Shad Thames Plaza [4]
The Tech Point is located on the roof of the building - simply use a drone to get there.
Rotherhithe Docks [5]
The tech point is hidden on the roof of the building. It's easiest to reach it using a drone.
Southwark River Gate [6]
The Tech Point is on the roof, under the grid. You need to use the Spiderbot to get it. There is a hole on the other side of the roof - jump inside and you will reach your destination.
Tidis [7]
The Tech Point is outside the complex, next to the terminal which opens the gates. You can get there by flying a drone.
Tidis Park [8]
The Tech Point can be found in the vent shaft on the roof of the building. Fly the drone there, then drop the Spiderbot, which will crawl inside the shaft.
Southwark Incinerator [9]
The Tech Point is located on the rooftop, next to the silos. It's easiest to reach it using a drone.
Southwark Auto Conversions [10]
The Tech Point is located on the roof of the building - simply use a drone to get there.
Around LDN Bus Depot [11]
The Tech Point is located on the canopy adjacent to the building. It's easiest to reach it using a drone.
Southwark Residential [12]
The Tech Point is in the construction zone. It is located on the tower.
St. George Church [13]
The Tech Point can be found in the vent shaft, on the roof of the church. To get there, you need to open the hatch, blocked by a circuit on the tower. Unlock it, then use the Spiderbot to enter the shaft.
Civil Aviation Traffic Office [14]
The Tech Point is on the rooftop. It's easiest to reach it using a drone.
Tidis Advanced Technologies [15]
The Tech Point is located on the platform adjacent to the building. You can fly up there on a drone, or you can get there from the building. If you choose the second option, then go to the very top and locate the moveable fan.
City Hall [16]
The Tech Point is inside the City Hall. You will find a locked room there, which can only be opened from the inside (using the Spiderbot). Your target is inside.
King's Head Yard [17]
The Tech Point lies on the pipes, on the roof of the building. It's easiest to reach it using a drone.
Guy's Hospital [18]
The Tech Point is located on the roof of the building - simply use a drone to get there.
Nexus Tower [19]
The Tech Point is inside the complex. You need to go to the very top of the complex. There, put the Spiderbot on the upper shelf and make it enter the vent shaft.
The Mix [20]
The Tech Point can be found in the vent shaft on the roof of the building.