There are very cool things you can do with DL. And the things you need to learn are not too difficult for basic NNs. Please don't dissuade someone's interests by saying they need the knowledge "from the ground up". Of course you will always have a "deeper" understanding any maths subjects if you start from the very beginning. But for me there was always so little context as to their use and application it was disheartening.

It will undoubtedly sound naive to some, but I've been preferring the ability to "drive the car" over how to build one from scratch. Using fastai and their book/videos I've been able to go from dropping calculus and quitting a web dev bootcamp to building an ML product in about a a year. (and would really be much fast if I didn't have repetitive strain injury)

GP, keep searching for your starting point.

Drive the car, learn to change the oil and brakes as you go. And if you're super interested, mod it and then make one.