no way to unzip and open rar files?

Seek out: The Unarchiver

https://www.keka.io/en/

Do you have homebrew? If so, you can install rar from there - brew install rar.

If you don't, could I suggest homebrew?

Rar is proprietary shitty file format made by russian for his own shitty archiver called winrar. Only way to unzip it is to use 3rd party software. "The unarchiver" works great for me, but you've told that it doesn't work for you