Not OP, but some channels I would recommend that work as audio-only: (mostly science or thought-provoking)

CaspianReport

CrashCourse

ExtraCredits

Innuendo Studios

Kurzgesagt

SciShow (and the sub-channels: SciShow Space and SciShow Psych)

PBS Idea Channel (no new videos, but old content is good)

vlogbrothers

Wendover Productions