I just found that they added "second screen" on S21 Ultra (ZVIH). I'm not sure if it's intentionally or accidentally because it is still said "tablet" on the page.
I've tried it on my computer and it works. I don't know if I will use it that often on my phone, but nice to have it.
My suggestion is that if Samsung intends to add this feature on phones, please also add a toggle in the quick settings panel too (just like on tablets).
