[SwissXC90]

Remove scuttle panel (plastic panel under the wiper arms, remove wipers first)
You will see the cabin air intake clearly
Clean out any visible debris everywhere

However the cabin air filter should be stopping debris from getting to the blower fan
Check that the cabin air filter is actually fitted!
Accessible behind a panel under the glovebox, remove some torx screws to drop the panel, then remove more torx screws to access the filter housing

But if the blower fan is off balance and vibrating, then you may need to replace the blower fan
This is a more involved job as more items need to be removed.
Officially, the entire dashboard must be removed
But there are ways of replacing the blower fan without removing the dashboard, if you break one mounting clip
Still an awkward job though. I've never done it.