Quest 3 v2.9: Sideloaded apps no longer support free window aspect ratio adjustment

After updating my Quest 3 to firmware v2.9, most sideloaded apps (including video players, streaming apps and remote stream tools) can no longer freely adjust their window aspect ratio.

When scaled up, their windows are locked to a nearly square shape and cannot be stretched to wide ratios such as 16:9.

This worked fine on older firmware versions before the update.

Is there any workaround for this issue?