TL;DR:

This build addresses a major performance issue that's responsible for the performance degradation we can measure during longer gameplay sessions.

--

Unfortunately, the new/current version of Unity has a bug in the culling algorithm of its closed-source engine section.
When used with the High Definition Render Pipeline, inactive lights are tracked by the rendering pipeline anyway. When these lights are later removed (typically during scene switches), it causes unhandled error spam in the rendering loop.

The core issue is in the closed-source section, but we've implemented a workaround that cleans up the leaking lights to prevent the degradation and error spam.