Guide Michael Tsang was able to take tourists freely around Asia’s financial hub in 2019, introducing them to the city’s protest movement, explaining “one country, two systems” and showing them scenes of economic inequality.

Since the coronavirus pandemic cut off foreign visitors and a sweeping national security law passed last year limited what Tsang’s tours could show, his business has been hit hard. So he shifted to attract local residents with activism tours, including the city’s LGBTI movement and refugee community...