Strangers - John Simm (2018) - Sham Tseng Sewage Treatment Works, Tsuen Wan

We get a much better view of the area in front of the "Kowloon Remand Centre" in Episode 8. Jonah goes there to visit the person responsible for all the murders and then meets up with Lau who wants to hang out until Jonah catches his flight back to the UK later that evening.

The area they are looking out to in the bottom image is the strip of sea between Lantau Island and the New Territories mainland (off screen to the right). Usually you would expect to see a plane preparing to land at the airport in the distance (approaching from the east) but I guess they timed the shot to avoid them.

Strangers - John Simm (2018) - Sham Tseng Sewage Treatment Works, Tsuen Wan

The "Kowloon Remand Centre" where the Triad is sent after being caught by the cops wasn't anything of the sort but in fact one of the Drainage Service Department's treatment works. This particular one is in Sham Tseng - located about midway between Tsuen Wan and Tuen Mun - an area famous in the past for its roast goose restaurants. This place is right down on the waterfront.