The drone playing is similar to the finger-picking in guitar playing. In finger-picking we try to play simultaneously, the melody and the underlying chords. In drone-playing the underlying chord is only one, note, the 1st or 5th of the underlying chord, or both. And these 1 or 5 are essentially open strings up or down to the string that we play the part in the current tetra-chord) of the melody.
Inverted ukulele tunings allow also for drone playing (Inverted tuning of G2C3E3A4 is the A2E3C4G4 , two 5ths and a 6th instead of two 4ths and a 3rd, which is more nice voicing of a minor 7nth chord)
The maximum abilities of drone playing seems to exist in the tunings like DADA or CGCG etc. but also such tunings inorder to give maximum abilities of drone playing (when playing a melody in a strings the other 3 strings can serve as harmonic drones, accompanying) they exclude the accompanying with ordinary major or monor 3-notes chords!!!. This forces a playing which is mostly melody (>70%) and little occupied with parallel harmonizing or chord-improvisation. Leonardo da Vinci used to sing and improvise, accompanying his voice with a continuous interval of 5th with a violin!
The drone-playing is the model of the ancient times' voice improvisation, accompanied only with intervals of 5th ot 8ths!!! (see e.g. https://www.youtube.com/watch?v=QUcTsFe1PVs&t=24s)
See e.g.
