[SDPhantom]

A lot has changed with how the TargetFrame shows auras.

local function TargetFrame_UpdateAuras(self)
    if UnitIsEnemy("player",self.unit) then
        for buff in self.auraPools:GetPool("TargetBuffFrameTemplate"):EnumerateActive() do
            local data=C_UnitAuras.GetAuraDataByAuraInstanceID(buff.unit,buff.auraInstanceID);
            buff.Stealable:SetShown(data.isStealable or data.dispelName=="Magic");
        end
    end
end
 
hooksecurefunc(TargetFrame,"UpdateAuras",TargetFrame_UpdateAuras);
hooksecurefunc(FocusFrame,"UpdateAuras",TargetFrame_UpdateAuras);

First to note, most of TargetFrame's functions were moved to a mixin. This is basically a table that is copied when inherited. The buff/debuff frames are now allocated by frame pools that provide a different way to iterate over them. Lastly, using .auraInstanceID, we can use the new C_UnitAuras.GetAuraDataByAuraInstanceID() to query the buff each individual button is assigned to.