Only really use Meridian endpoints, mostly MS200s, and a 218.
Not at home so can’t grab screenshots, but normally to power off zone(s) I think you click on the speaker/volume icon at the lower right, and in the popup there is a power icon, for a single zone when you click on it that it turns red and the zone powers off. For a group when you click on the power icon it used to expand to show power icons for all the zones in a group, and you could click on them one at a time to turn them off (they would also turn red). Now when you click on the power icon for a group it does not expand, nor does it turn red or turn anything off. Workaround is to ungroup the zone you want to turn off, then you can turn it off. Actually the way it used to work was kind of silly, having to turn off each “member” of a group individually. Would be better if you could just turn off all zones in a group with one click …
Click on the power icon and the row for the top icons gets a little fatter, but no power icons for zones (like in 1.7), and not possible to turn the group off.