local TextChatService = cloneref(game:GetService("TextChatService"))
local isLegacyChat = TextChatService.ChatVersion == Enum.ChatVersion.LegacyChatService
local function SendMessage(message)
    message = tostring(message)
    if not isLegacyChat then        TextChatService.TextChannels.RBXGeneral:SendAsync(message)
    else      ReplicatedStorage.DefaultChatSystemChatEvents.SayMessageRequest:FireServer(message, "All")
    end
end
SendMessage("chat message")