Learn Portuguese (Portugal): Os fãs rivais não conseguem lidar uns com os outros. - The rival fans cannot deal with each other.

In Portuguese, when a reciprocal action requires a preposition (like com for the verb lidar), the preposition splits the reciprocal phrase. Instead of grouping the words like 'with each other' in English, Portuguese structure literally says 'some with the others' (uns com os outros).

Could I say um com o outro instead of uns com os outros here?

You would use um com o outro if you were talking about exactly two fans. Because fãs implies a larger group here, the plural form uns com os outros (with one another) is the correct choice.

Is the word fã always masculine, as in Os fãs?

No, fã is an invariable noun, meaning its spelling never changes, but its gender depends on who you are talking about. If the rival fans were exclusively women, it would be As fãs rivais and the reciprocal phrase at the end would also change to feminine: umas com as outras.

Why use conseguem rather than podem for "cannot"?