Belarus adds an opponent on the north that Ukraine can’t really afford to open up. Again Ukraine doesn’t have the men for a two or three front war.
Like posted, it is most likely a counter assault to pull Russian resources off of other places. Or an operation to take out something local of strategic value.
Bialorus was already a combatant right from Feb 2022 — remember that the initial “head thrust” to Kyiv was launched from Bialoruski territory.
As to the Bialoruszyni themselves fighting - that is not going to happen. The simple reasons why this is NOT going to happen are:
1. The Bialoruski military is a joke, they are kept weak so they can’t overthrow Lukashenko.
2. The Bialoruski people do not want anything to do with this war - they don’t want to die for either side