Posted By Joe Craig on 29 Aug 2019 01:26 PM
Inventua is still around, and they seem to have a version of SideMenu that works for DNN 9. You might want to contact them for options (http://www.inventua.com).
That was the first menu I used in DNN as menu at the time horrified me.
I'm amazed they have a DNN9 compatible version, but as you stated, replcing it with DRR is quite easy.