There is a LOT of information on the web on getting started with React-Native.
There is a LOT of misinformation on the web on getting started with React-Native.
Some of the misinformation exists because it was once correct, but is now dated.
Some of the misinformation exists because it showed how to "get something working", but it doesn't really understand/explain why it works (and thus is often not really correct).
Some of the misinformation exists because it confuses several issues.
Examples of misinformation about React-Native:
React-Native cannot perform well
always "eject" your project
"eject" makes you more productive/gives you more options
React-Native only works on iOS and Android
React-Native only works on phones
All of the above is wrong to one degree or another.
When it comes to info about React-Native (and Expo!), I encourage my team to look for recent info and to ignore older info. Expo and React-Native in particular have evolved rapidly and the pace continues to increase. The release of Expo SDK 48 is full of new features and up-to-date libraries.
My advice is to ignore any information published more than 9 months ago. Look for newer sources.