Focus in any VR headset is per the headset directions/instructions. Many don’t have focus adjustments or you set the distance from eye to lens mechanically.
In sim there are ways to change the image resolution/clarity but that is different from focus.
Looks like the available adjustments are image resolution/clarity settings.
Rift S mechanical visual focus does not improve focus adequately.
Resolution & Clarity adjustments may help (viewing the display readouts on the panel in the cockpit
is still somewhat diffused/lacking sharp definition).