Step 1: install the mod with neoforge 1.20.1-47.1.106

The newest possible allowed marked and flagged version for neoforge is 1.2.15 as seen https://www.curseforge.com/minecraft/mc-mods/immediatelyfast/files/all?page=1&pageSize=20&version=1.20.1&gameVersionTypeId=6

Step 2: Try to run minecraft

Step 3: it fails

Full crash report https://pastebin.com/kA586852

Snippet of error

Details: Mod File: NO FILE INFO Failure message: The Mod File C:\Users\lothr\AppData\Roaming\gdlauncher_carbon\data\instances\neoforge 1.20.1\instance\mods\ImmediatelyFast-NeoForge-1.2.15+1.20.4.jar has mods that were not found Mod Version: NO MOD INFO AVAILABLE Mod Issue URL: NOT PROVIDED Exception message: MISSING EXCEPTION MESSAGE
Screenshot

This error goes away if you use ImmediatelyFast-Forge-1.3.4+1.20.4.jar with neoforge. However the curseforge app incorrectly marks this as "not for neoforge, only for forge" when it actually seems to run fine in neoforge.

NeoForge 1.20.1 is really just Forge, but renamed. The NeoForge version of ImmediatelyFast is for NeoForge, where they actually started deviating from the Forge casebase (This is 1.20.4 and above). The new Forge versions of ImmediatelyFast for 1.20-1.20.4 are not marked as NeoForge compatible, because they only work on NeoForge 1.20-1.20.1 and it would require making seperate releases to break the version range into two (Which would break my auto publishing workflow). I won't make seperate releases for this case because it affects a very very small userbase which still use NeoForge 1.20.1. You can safely use the Forge 1.20.1 version on NeoForge