As far as I know, words ending with -un do not denasalize when they participate in a liaison, which is rare.

The liaison is mandatory with un, aucun, commun

Un avion ɛ̃n‿avjɔ̃ or in a wide Paris area œ̃n‿avjɔ̃

D’un commun accord komɛ̃n‿akɔʁ or komœ̃n‿akɔʁ

Aucun artiste… okɛ̃n‿aʁtist or okœ̃n‿aʁtist

but forbidden with most if not all other words in -un like chacun, embrun, importun, opportun, jeun.

Chacun arrive… ʃakɛ̃ aʁiv

Words ending with -um do not nasalize in the first place. They are pronounced -ɔm , e.g. album albɔm

There is a unique exception : parfum parfɛ̃ or parfœ̃ which never liaises.

The cases of denasalization in French seems to be limited to finals in [ɛ̃] and [ɔ̃].

Ancien ami ɛ̃sjɛ̃n‿ami, ɛ̃sjen‿ami or ɛ̃sjɛn‿ami

Son ami sɔ̃n‿ami or sɔn‿ami