You can check my YouTube playlist. I have created it, especially for beginners.
NiFi the Complete Guide
After finishing my YouTube tutorial, if you wish to dive deep into the advanced topic, you can opt my Udemy course.
Apache NiFi - The Complete Guide (Udemy Course)
You can learn the same course in Skillshare for FREE using the below referral link.
Apache NiFi - The Complete Guide (Skillshare Course)