https://build.sailfishos.org/ is running again 
Older SFOS releases aren’t yet available but 4.0.1.48 is there … with aarch64
We also have a ‘Chum’ repository which was intended to be a place for developers to release apps for the community to install from. (For those of you who remember maemo-extras and maemo-extras-testing)
The intention is that apps built on the OBS can also be built in Chum and users just add the one repo to be able to install any of the apps.