Pywavelets CWT returning 0 after scale 64
PyWavelets' cwt is flawed, and so is scipy's; use ssqueezepy.cwt.

a low pass for the lower frequencies not covered using the mother and daughter wavelets
... with the short time Fourier transform of lower frequencies in one graph

This is exactly what kymatio's Scattering1D does (pass average=False, oversampling=999), it's CWT for most frequencies, and STFT for lowest,
and one row dedicated to lowpass. Kymatio's CWT is identical to ssqueezepy's but with different filter design (more efficient for ML).