It is not obvious from your question if you come from an academics perspective or a foreign language learner perspective.
If you just want to know how the sentence is pronounced, the answer proposed as duplicate by several commenters has ample enough information.
From a phonetic point of view, here's what I found: there is always an enchaînement, in the linguistics sense, when a word ends with a consonant and the next begins with a vowel sound. See explanations here, there.
Si le premier mot finit par une consonne prononcée et que le mot suivant commence par une
voyelle, la consonne finale s’enchaîne au mot suivant comme une attaque.
In your example, as "plus" is a noun (last bullet point of case 2 in the duplicate answer) so the final consonant "s" is always pronounced, and as the next word begins with a vowel, there must also be an enchaînement.
The end consonant is recombined into the syllable of the next word, which makes it [ply.sɛ̃.de.njabl]
.
It is similar to:
Un abribus aérien
Un prospectus emballé
etc.
I've learned that there should not be an enchaînement
I'm not sure why, from a linguistics point of view it seems to be a misunderstanding.
I think there are indeed many people who would avoid the enchaînement
I'm not sure about "many" people, but maybe some do it because they want to emphasize "indéniable" and they pause slightly between the words. It is definitely not a rule (or an identified exception to the rule) - actually you'll hear a thousand shades of pauses or emphasis in the wild... it's the difference between theory and practice.