With no major change in the 1.20.6, most 1.20.5 mods are compatible with it, but looks like NeoForge removed the FinalizeSpawn method in 20.6.50-beta.

Minecraft version: 1.20.6
Modloader: NeoForge
Forge version: 20.6.72
Environment: Singleplayer
Mod version: guardvillagers-2.1.1-1.20.5.jar

Hate to say it but I'm gonna have to port straight to 1.21 and ignore 1.20.6