“Is ohm’s law universally applicable?”
The Ohm’s law states that “The current through a conductor is directly proportional to the potential difference applied across its ends provided the physical conditions such as temperature remains the same”
From the statement it is implied that it is not a universal law, and is applicable to conductors. It is not valid for semiconductors and electronic devices.
The substances which obey Ohm’s law are said to be ohmic and those which do not obey Ohm’s law are “Non Ohmic“