testing branch contains packages to make use of Virtual Reality on Alpine Linux so make sure that is enabled.
You will need an OpenXR runtime to run any applications on VR.
Monado itself includes some required drivers, and it'll also pull in OpenHMD and libsurvive which provide drivers for the HMD and positional tracking respectively.
Any application that requires VR should automatically pick up your HMD.
You can use xrdesktop to interact with your desktop windows in VR if you're running KDE Plasma. Support for GNOME is in the works but as of now requires patches on top of GNOME which aren't packaged on Alpine.
Make sure to enable
xrdesktop in the settings,
Workspace -> Workspace Behaviour -> Desktop Effects -> xrdesktop.
Optionally you can install a Plasma applet to easily toggle VR mode.