This is not an ad it’s just an user experience. Long story short, I couldn’t find an actual software that converts nef to jpg without buggy results.
I eventually found a software called RawTherapee. It’s free.
Enter the software. In the bottom-left corner you can find a folder to be converted. Double click it. Click one photo press Ctrl+A to select all and then right click the mouse and select Put to queue. In the top-left part of the software you can see 3 tabs and press Queue.
Where we have 3 you can choose the format and quality. Just leave it as is. In the 2 zone, you can choose the folder where the jpg will be saved and 1 shows a switch which you press and it will automatically convert your photos. And that’s it!
After this, you can also use this free tool on the Microsoft Store, to resize the pictures: Resize Image software. It keeps the quality and it makes the file smaller, perfect for uploading on websites or storing hundreds of photos from a wedding or stuff like that. Good luck!