setting vertical justification except for last page of a chapter

As @James Gifford—NitroPress says, there's no way to top-align the last page of a chapter automatically in InDesign.

But you may want to check out my (not free) script Unjustified: https://www.id-extras.com/products/unjustified/

It's not really good practice to use vertical justification throughout a document. Yes, you get even bottom alignment, but at the cost of varying spacing across each page.

That said, the only way to have different alignment on a last page is to set it manually on that text frame, which should be a one-time, before-print action.