I personally think the best way to learn it is to get your hands dirty and use it to build something, so I'd recommend that, but there are certainly resources out there as well.
This sounds like an excellent bug report for their playground feedback[0] repository, I'll make a ticket for you[1], please feel free to go in and fill out more information to help them help you.
Please note that the links in the issue you submitted need to be changed because you copied the link text, which are only partial, rather than copying the link target URLs.
https://www.nativescript.org/
Here's a talk from 2 years ago:
https://www.youtube.com/watch?v=ELemwZXJZVg
I personally prefer Nativescript-Vue and I find their docs to be very good:
https://nativescript-vue.org/en/docs/introduction
Some more video resources:
https://www.youtube.com/watch?v=DcCSq2Y9bow
https://www.youtube.com/watch?v=qR1ESQTALI0
I personally think the best way to learn it is to get your hands dirty and use it to build something, so I'd recommend that, but there are certainly resources out there as well.