rEFInd is not working in macos high sierra 10.13.6 on 2018 MacBook Pro 13 inch even after proper installation
EDIT: You'll have to run the ./refind-install program in macOS after you've run csrutil disable in the Recovery OS. This will most likely solve any issues you have with installation.

Original answer: I think your problem is that you've tried to disable csrutil through a terminal in MacOS, which won't work. Try following the steps in this article to go into Recovery OS, run csrutil disable; reboot in the Terminal, and then try going through the normal refind install steps. It's your choice if you want to re-enable System Integrity Protection afterwards, but again you'll have to do it through Recovery OS.

Hopefully this advice was interesting and useful to you, and I wish you good luck.