Can jinn be Muslim?

Yes, clearly and explicitly. Surah Al-Jinn records a group who heard the Quran, recognised it as truth, and believed. They describe themselves as having previously held false beliefs, and they go on to warn their people.

Surah Al-Ahqaf records a similar account. Al-Jinn also states that among them are the righteous and others, that they follow differing paths.

This should change how the subject is discussed. Jinn are a species with the same moral range as ours. Among them are believers who pray and fear Allah, disbelievers, and everything between.

Using the word jinn as though it means something malevolent is roughly as accurate as using the word human that way. Iblis and the shayateen are a specific category, not the whole species.

Practically, this matters because fear generalised to an entire creation of Allah is disproportionate. The Quran mentions them, establishes their accountability, prescribes protection from harm, and moves on.