I am using Prisim Launcher and OPAC b0.23.0 on NeoForge 1.20.6, OPAC is the only mod installed and i get java.lang.NoClassDefFoundError: net/neoforged/neoforge/event/entity/player/EntityItemPickupEvent Error, i am attaching my full log
latest.log

Thanks for reporting!
Kind of strange because I can see that they have removed this class but when I download the latest version of NeoForge it's still there.

Fixed in 0.23.1.