According to Jain philosophy:

• When a soul attains moksh (i.e., all karmas are completely destroyed), it becomes totally light and pure.
• At that very last moment of life, the soul rises straight to the top of the universe (Siddhashila).

Scriptures describe this as an instantaneous ascent from the place of nirvana (earth, or wherever that last life ends) to Siddhashila. It is not like a slow physical travel taking minutes, hours, or years. Once all karmas are destroyed, the soul, by its own nature (very light, upwards-moving when free), immediately reaches Siddhashila and remains there forever.

So in simple words:

• Time taken from earth to Siddhashila after moksh: instant / momentary, not a long journey.
• Both Digambar and Shwetambar accept this same basic idea; differences are only in detailed cosmology drawings or descriptions, not in the fact of instant ascent.

You can read more about Siddhashila and liberated souls here