Maybe there are better than Manjaro arch based starter distros, but for getting someone into Linux, my experience with Manjaro was great.
When the manual doesn't work (The most recent installer ISO I was using had versions of some commands where what the wiki said to do wasn't a valid flag) you're really gonna have a bad time. Especially when, as is seemingly often the case, you don't realize that the command you ran didn't do everything it needed to until 4-5 commands later when something entirely different fails.
I can imagine it's easier to install on older~ hardware with no dual boot though.
You don't have to bother with even that nowadays (except maybe to connect to wifi before installation). Arch ISOs nowadays come with an easy, self-explanatory TUI installer with which you can install it just as easily as you would install Ubuntu.