Storeman Installer
https://github.com/storeman-developers/harbour-storeman-installer

Storeman Installer works on any SailfishOS release ≥ 3.1.0 and on all CPU-architectures.

Older Storeman releases, which work on older SailfishOS releases (e.g., v0.1.8 on SailfishOS 2.2.1) are available at:
https://github.com/storeman-developers/harbour-storeman/releases

Note that, before software can be built for a SailfishOS release at the SailfishOS-OBS, Jolla must create a corresponding "download on demand (DoD)" OBS-repository.  It often takes some time after a new "general availability (GA)" SailfishOS release is published before the corresponding "DoD" repository is being made available, during which installing or updating Storeman by the Storeman Installer or Storeman's self-updating on a device with the new SailfishOS release already installed will fail; consequently this is always the case during the "closed beta (cBeta)" and "early access (EA)" phases of a new SailfishOS release.  Hence one has to manually download and install or update Storeman built for the last prior SailfishOS GA release, then.

Issue tracker & source code repository:
https://github.com/storeman-developers/harbour-storeman-installer