Delete / Comment the following things on each .aspx page in the current “portal template” folders.
<%@ Register TagPrefix="dnn" TagName="ACTIONS" Src="~/Admin/Containers/Actions.ascx" %>
or
<%@ Register TagPrefix="dnn" TagName="ACTIONS" Src="~/Admin/Containers/SolPartActions.ascx" %>
AND
<dnn:ACTIONS runat="server" id="dnnACTIONS" ProviderName="DNNMenuNavigationProvider" ExpandDepth="1" PopulateNodesFromClient="True" />
or
<dnn:ACTIONS runat="server" id="dnnACTIONS" />
because,
They remove the following navigation providers in DNN 8+ versions
ASP2MenuNavigationProvider DNNDropDownNavigationProvider DNNMenuNavigationProvider DNNTreeNavigationProvider SolpartMenuNavigationProvider
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