Hello.
I installed OTB 6.6.1 yesterday with QGIS 3.8 and the tools were in the toolbox. I ran a tool and it worked. I was happy. I installed it using this youtube video as a guide because I couldn’t figure out how to install OTB without it: https://www.youtube.com/watch?v=Jl_G1XIblJs
I then closed QGIS. I then reopened the same QGIS project but now I cannot see the OTB tools in the toolbox. I have completely removed OTB from its C:/ drive installation location and reinstalled it and restarted the plugin. Nothing works. The plugin is still listed but the OTB tools are not in the toolbox. Where have they gone?
The plugin is in QGIS by default now (see QGIS 3.8 release notes). So to use OTB in QGIS you should only have to configure OTB in Settings/Options/processing (I had to remove my local qgis-plugin from QGIS to make it work).
I had originally installed OTB to my C: drive but I have now removed it from the C: drive. At a different time (and currently) it is in my ‘software’ folder (see below image) and it still points to the location on my D: drive. But it works!