As adjectives the difference between unpreachable and unreachable
is that unpreachable is not preachable; impossible to preach while unreachable is unable to be reached; impossible to attain.
As a noun unreachable is
a person or thing that cannot be reached.
unreachable
English
Adjective
(-)
Unable to be reached; impossible to attain.
Noun
(
en noun)
A person or thing that cannot be reached.