[Walkerbo]

Hi Fizzlemizz

You are right.

local f = CreateFrame("Frame")
f:SetScript(
    "OnEvent",
    function(self, event, ...)
        if event == "UNIT_SPELLCAST_SUCCEEDED" then
            _, _, spellID = ...
            mountID = C_MountJournal.GetMountFromSpell(spellID)
            for k, v in pairs(C_MountJournal.GetMountIDs()) do
                if v == mountID then
                    Dismount()
                end
            end
        end
    end
)
 
f:RegisterEvent("UNIT_SPELLCAST_SUCCEEDED")

Thanks for your help.