I've tried denyHoppers false in lwc, in spigot.yml hopper ticks for transfers and checks are both 8 & hopper-amount is 1, hopper removed from blacklisted blocks in lwc, nothing I try allows players to have a hopper feed into a chest.
Weirdly enough it works perfectly for me (I place a hopper on top of a chest, it goes in, no messing about with silly hopper on commands) as owner/op, but when I remove my op and owner perms it still works for me (even replacing them). But nobody else can do it (even when they try the /chopper on etc), I'm really just lost for ideas at this point and wondering if anyone had any experience with these issues? Is it world guard? Some sort of spigot/paper/bukkit config issue? I think insights also limits chunks to 20 hoppers, is that related?