Official and high-quality instrumental versions can be found on several platforms:
The signature "flute" sound used in the track is an Idian Bansuri Flute preset, often processed with a filter and portamento/legato settings to create a gliding effect between notes. Armani White - BILLIE EILISH. (Instrumental)
Armani White - BILLIE EILISH. (Instrumental) (Karaoke Version) YouTube · ZZang KARAOKE Where to Listen Official and high-quality instrumental versions can be found