All I can think is using a third party launcher. For example nova launcher or one of the others. It is a shame galaxy themes are not on Samsung tablets. Something I think they should bring in the future.
I used Samsung's good lock theme park module to create a theme on my Tab S8 ultra. You can create main brilliant themes and change nearly all aspects of the them, text, SMS text boxes, quick panel icon colours etc. I think that's the only way to get a theme on Samsung tablets. It worked for me 😁👍