@SteveRiggs Here are a couple of courses I encountered on my search for more DSP and C++ for Audio resources:
Kadenze - Advanced Audio Plugin Development with C++ in Juce (by Output)
Not sure about the content quality, but it seems ok for beginners. The Basic Course is free btw...
Hack Audio - Creating Audio Plugins with JUCE
Purchased it, but it's very basic tbh.
However the Hack Audio DSP book is quite interesting:
Hack Audio: An Introduction to Computer Programming and Digital Signal Processing in MATLAB
The DSP courses on Coursera are good as well. they are mostly free, so it doesn't hurt to take a look at them.