Explain your idea

As older than 1.21 issues posting is closed I did it like this, sorry about that.
I was using ImmersiveEngineering-1.20.1-10.1.0-171 which was working fine with NeoForge 47.1.106

As final version 10.2.0-183 of IE was released for 1.20.1 I wanted to update to it but it calls for Forge 47.3.0 during loading.

Would it be possible to make it work with NeoForge again?

NeoForge for 1.201, has been delisted and is no longer available for official download.
I have been effectively bullied by various other people in the community to make IE for 1.20.1 compatible with Forge instead.

I'm not happy about it (as my commit on the matter should show), but I got tired of fighting people. I'm sorry for a final bit of inconvenience, but I just wanted to be done with that fucking version and never touch it again.

If you wanna make the best possible choice, honestly, move to 1.21.1. It's where our focus is, where the new features are, and it's guaranteed NeoForge only.