Many diplomats and international civil servants posted to Geneva live in France. (I didn't, but then my Mission paid my rent. I lived in Vessy.)
I recall a notorious instance when an Algerian diplomat accredited to the UN was stopped and investigated (!) at Meyrin or environs. Scandalous: he would have had the same Carte de Légitimation I had, but perhaps not Swiss diplomatic licence plates. And of course he would have spoken fluent French.
There has to be a personnel office at the UN that knows what to do and will do it.
Here's a page on the taxation status of UN staff as to France:
https://www.diplomatie.gouv.fr/fr/em...internationaux
Also not relevant to your question directly, but relevant to your status:
https://www.eda.admin.ch/missions/mi...immunites.html
This essay doesn't answer your question but does survey the universe of frontier workers
https://www.unige.ch/sciences-societ...erEnSuisse.pdf
Presumably like me you have employer-sponsored private health insurance. If not, read this:
https://www.cleiss.fr/particuliers/j...en_suisse.html
Here's a real estate agent's view:
https://www.agence-immo-ds.com/ou-ha...se-geneve.html