Trying to install Black Flag in Foundry VTT fails

[DrHolzer]

I am trying to install the Black Flag system in Foundry and it gives me the following error in the console:

tup.js:292 Error: Unable to load valid system manifest data from "https://github.com/foundryvtt/black-flag/blob/main/system.json"
The requested manifest at "https://github.com/foundryvtt/black-flag/blob/main/system.json" did not provide system manifest data.
    at Module.installPackage (file:///home/foundry/resources/app/dist/packages/views.mjs:1:1634)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at async SetupView.handlePost (file:///home/foundry/resources/app/dist/server/views/setup.mjs:1:1980)