Scales to Play Over Dm7b5
Every chord is a subset of several scales: any scale that contains all of a chord's tones fits over it. Pick a chord to see the matching scales from its own root, the major keys the chord belongs to, and full fretboard diagrams for every scale on guitar.
A Dm7b5 chord contains the notes D – F – Ab – C. Any scale that includes every one of those 4 tones fits over it — from the root D, that means D Blues, D Locrian, D Half Whole Diminished and D Gypsy Major. They differ only in the notes between the chord tones, and that is where each scale gets its color.
Dm7b5 is also diatonic to one major key: Eb major (relative minor Cm). In a song from one of those keys you can also solo with the key's own major scale or its relative minor pentatonic across the whole progression, not just this chord.