Recommendation

[Sylar]

Update to Unity 6 version. As the current version of the build is still December of last year.
Utilise the new GPU Resident Drawer and GPU Occlusion Culling.
They included a new Render Graph API for URP.
Improved Fixed Foveated Rendering for PC and Gazed for VR users.
Also the new Unity 6's Adaptive Probe Volumes (APV) allow you to build time-of-day in-game scenarios, which would be great for the story.

APV Sky Occlusion could also help the starlight movements to vary the ambient lighting in subtle but beautifully elegant ways. This could be useful for making star positions relevant to unlocking secrets in a very large world devoid of auxiliary stories.

APV Scenario Blending will also help smooth out some of those janky day–night light transitions and other lighting issues, and make the red flare reach farther in caves to blend a lot better with ambient surfaces.

Probe Adjustment Volumes tool will fix light leaking situations to create better effects. Like when entering or exiting a cave, you would be able to see from the inside of the cave whether it's day/night outside as you approach the entrance/exit.

Unity 6 also added "ozone layer support and atmospheric scattering to complement fog at long distances." Which I think would be amazing. The new C# Light Probe Baking API will help balance lighting impact. Underwater Volumetric fog has also brought great improvements for the new Unity 6.

Finally, with the new update, there really is no excuse for not having houseboats/rafts, as well as fixing the lack of sinking when falling from great heights (can be adjusted relative to fall time) for better physics when dropping from a glider.