Learn Hardcore Norwegian: Hun er enig, men han er uenig i detaljene. - She agrees, but he disagrees on the details.

jeg er enig (I agree), past jeg var enig
To talk about reaching agreement: vi ble enige or å bli enige om noe (we came to agree on something)

How do the prepositions with enig/uenig work: med, i, and om?

They signal different relationships:

enig/uenig med [person] = agree/disagree with someone (a person)
enig/uenig i [påstand/argument/detaljer] = agree/disagree with a statement, argument, or parts/details of something
enig/uenig om [tema/sak/detaljer] = be in (dis)agreement about a topic/issue/details (the matter under discussion) All three are common; choose based on what you’re linking to: person, content, or topic.

Is i detaljene the only option, or can I say om detaljene?

Both i detaljene and om detaljene are idiomatic.

i detaljene highlights the disagreement “in the details themselves” (inside the finer points of a plan/argument).
om detaljene treats the details as the topic they disagree about. Many speakers default to om here, but your sentence with i is also fine.

Do enig/uenig change form for gender or number?

In the singular, enig/uenig do not change for gender or neuter: han/hun/barnet er enig/uenig.
In the plural they take -e: de er enige/uenige.
Note: No neuter -t form is used (*enigt is not used in modern Bokmål).

Why is it detaljene and not detaljer? What are the forms of “detalj”?

detaljene is the definite plural (“the details”), implying a specific, known set. Use detaljer (indefinite plural) for details in general. Forms:

en detalj (a detail)
detaljen (the detail)
detaljer (details)
detaljene (the details)

Why is there a comma before men?

men (“but”) is a coordinating conjunction joining two independent clauses, and Norwegian convention places a comma before it: …, men …. Your comma is correct.

What’s the word order after men? Could it be “men er han uenig”?

After men, you start a new main clause with normal main-clause order: subject first, then the finite verb. Hence men han er uenig.
If you front an adverbial, the V2 rule still applies: Men i detaljene er han uenig (adverbial – verb – subject).

Can I use mens instead of men?

Yes, mens (“while/whereas”) is possible: Hun er enig, mens han er uenig i detaljene.

men = simple contrast (“but”)
mens = contrast with a “whereas/at the same time” nuance

Is there any difference between uenig and ikke enig?

Both are correct, but uenig is often felt as a bit stronger or more direct. ikke enig can sound slightly softer or non-committal. Word order with negation: Han er ikke enig i detaljene.

Are there alternative pronouns to hun and han?

hun (she) and han (he) are standard Bokmål.
hen is a gender‑neutral singular pronoun increasingly used in Norwegian.
ho is common in many dialects and in Nynorsk.
hu is a colloquial spoken variant of hun in some areas but not standard in writing.

Is uenig written with a hyphen (u-enig)?

No. The negative prefix u- attaches directly: uenig. No hyphen.

How do you pronounce the tricky words here?

Approximate guide:

hun: “hoon” (fronted u)
er: “air”
enig: “AY-nee” (g often silent)
uenig: “oo-AY-nee” (two syllables: u‑enig)
men: “men”
han: “hahn”
detaljene: “deh-TAHL-yeh-neh” (the j is a y-sound)