TN to GreenCard

I have browsed through the forum and I have noticed that it has been repeated many times that there is a way to apply for green card while on TN (without getting a H1) but no one has actually provided a way of doing so. I am wondering if it this is true and legal and if so, can some one please educate us on the process.

There is a huge risk in TN to green card since TN is a non-immigrant visa and filing green card contradicts that intent.

One may risk TN visa cancellation in event of green card filing without switching to H visa.

Now that TN visa is for 3 years, it is better to switch to H visa in April and then file for green card.

If TN is now 3 years, doesn't it make it now a dual-intent visa? If it does, then why is there a "huge" risk in applying for green card from TN?

no, it is still not a dual-intent visa. It is a temporary 3 year visa that allows you to live and work in the US for the duration, it is not specifically allowed to apply to adjust status to permanent resident.