KDE Plasma, the desktop DE, is kind of like GNOME, yes. Same with XFCE, Mate, Pantheon, and many others. Different look and feels, different workflows, different people working on them. All accomplish mostly the same thing though.
I’ve never tried this site personally, but you can test a distro running KDE Plasma (among many others) at this site: https://distrotest.net/KDE%20neon
Just if you’re curious.
Plasma Mobile, on the other hand, is quite good, but Phosh is excelling, as people have pointed out here, probably mostly due to Purism’s corporate backing.
Phosh is paid for by Purism.
Plasma Mobile is (as far as I know) only volunteer work.
@amosbatto had a great write-up on why Phosh is likely to succeed as a mobile DE from a while back: The strategic advantages of Phosh for mobile Linux