Chosen Solution

Hello, I have a question, nothing difficult, I uncovered my iMac 21.5 Late 2012 13.1 and I see that it has a port where an NVMe SSD can be placed, remove the doubt, I can place one

Why not? Make sure you use the correct drive MPN: 661-7108 or similar

Here’s the iFixit guide iMac Intel 21.5" EMC 2544 Blade SSD Replacement And here’s a great reference on what you’ll need for a replacement blade SSD The Ultimate Guide to Apple’s Proprietary SSDs