Which Ultra did you get? A Tab Sx Ultra or a S2x Ultra smartphone? You download the Good Lock app from Samsung's store (it's a Samsung app, not third party) then within the app is another app called Good Home. Download that and then you can make customisations to the Home Screen etc. In there you should be able to increase the amount up to 9 favourites if it's the S23 Ultra (maybe all S phones can do this I've just never tested).
At the moment for me the Tab S9 Ultra is limiting me to 8 home screen app favourites. In the app the area where it says 14 home screen app favourites max, it is greyed out. I'm waiting until an official release comes available but someone has said there is an apk available for a newer version online that fixes the issue.