Quick take
Yes, RO can reduce fluoride. For a purchase, verify that the exact finished system has a fluoride-reduction claim under NSF/ANSI 58 or equivalent model-specific testing.
Why RO can reduce fluoride
RO forces water through a semipermeable membrane that rejects many dissolved ions. CDC lists fluoride among chemicals that RO may reduce.
What NSF/ANSI 58 tells you
NSF/ANSI 58 includes an optional fluoride-reduction claim. A system certified to Standard 58 does not automatically have every optional claim, so check the model listing.
Why TDS is not fluoride proof
A lower TDS reading shows broad dissolved-ion rejection but does not prove a particular fluoride concentration. If fluoride is the treatment objective, use a model-specific performance claim or post-treatment test.