Sitemaps haven’t changed in this regard. So if you are using a sitemap it works exactly the same.
If you want to use the new MainUI, then you’ll have to either find (Universal widget for switch, dimmer, color items and Neato Vacuum Control look promising) or design your own widget. Not that it somewhat depends on whether you want this widget to be used in the automatically generated parts of the overview page (Locations, Equipment, and Properties) or if you want them to be used on a custom page you build yourself.
MainUI is a whole new UI with bears almost nothing in common with sitemaps.
It does work the same.
And for a last bit of advice. Those users who have the worst time getting started with OH 3/4 are not new users or non-technically inclined users. It’s OH 2 users who skip the Getting Started Tutorial who have the most trouble.