In case anyone is looking for DSP textbooks:
I’ve been using Paolo Prandoni and Martin Vetterli’s Signal Processing for Communications as a DSP reference for a few years, and I just learned the authors have also released it for free online: https://sp4comm.org/getit.html
I like this book since it’s got a good balance between theory and practical application, and has fun examples and exercises.
Hopefully this is useful for others as well!