In 1.18+, because of the terrain changes, the skybox will need to be created at a dynamic height to spawn players at a reasonable height in both mountainous and flat terrain.

Simple solution:
Find the lowest ground directly below spawn and create skybox x blocks above - This has already been implemented in a private development branch.

More advanced:
Try to find the highest ground elevation in a certain area around the skybox and adjust height based on that to prevent a nearby mountain from blocking the view.

There might be more edge cases where the spawn is right above a big cave opening in a mountain. Previous versions spawn dirt pillars for any air block below spawn and below sea level. This is probably not going to be sufficient for any 1.18+ release

Beyond that, I would like to give players the ability to enter a form of skybox before the terrain generation is completed to give them the ability to evaluate the spawn point sooner, and possibly skip cards sooner. This skybox could also include a big version of the card, similarly to the lobby (possibly in the ceiling to avoid occluding the view in one direction).

Feedback of 5.1 beta versions should conclude the final implementation.